Biomedical subjects

Russell Chess-Williams

Publications and source records attributed to Russell Chess-Williams.

At least 19 recordsLinked to original sources

PubMed2006

Depressed contractile responses to neurokinin A in idiopathic but not neurogenic overactive human detrusor muscle.

OBJECTIVE: The role of tachykinins such as neurokinin A in regulating bladder function is unclear, but NK2 receptors seem to mediate contraction in the human bladder and it has been suggested that these peptides may have a role in the pathophysiology of bladder dysfunction. The present study investigates neurokinin receptor-mediated contractility of detrusor muscle in the idiopathic overactive and neurogenic overactive bladder and investigates the neurokinin receptor subtypes involved. METHODS: Human bladder was obtained from patients undergoing cystectomy (normal) or clam cystoplasty (idiopathic overactive) and from patients with spinal injuries (neurogenic overactive). Strips of isolated detrusor muscle were mounted in physiological Krebs-bicarbonate solution and cumulative concentration-response curves to 1 nM to 300 microM neurokinin A (NKA) were obtained in the absence and presence of neurokinin receptor antagonists, either the NK2 receptor-selective antagonist SR 48968 or the NK3 receptor-selective antagonist SB 223412. RESULTS: NKA evoked concentration-dependent contraction of normal, idiopathic, and neurogenic overactive detrusor strips. In idiopathic overactive detrusor muscle, NKA-induced contraction was significantly reduced relative to normal detrusor (0.031 +/- 0.005 mg/g, n = 11 versus 0.193 +/- 0.039 mg/g, n = 7). Sensitivity to the peptide was also significantly (p < 0.01) reduced in idiopathic overactive detrusor, with mean pEC50 values (concentration producing 50% maximal response) of 6.62+/-0.16 (n = 11) compared to 7.47+/-0.19 (n = 7) in normal detrusor. In contrast, NKA-induced responses of neurogenic overactive detrusor were similar to those in normal detrusor, with a mean maximum contraction of 0.199 +/- 0.036 mg/g (n = 10) and mean pEC50 value of 7.85+/-0.16 (n = 10). NKA curves in all groups were shifted to the right by the NK2 receptor-selective antagonist SR 48968 with high affinity, pK(B) values being similar in normal, idiopathic, and neurogenic overactive detrusor (8.85 + 0.08, n = 14; 8.97 +/- 0.13, n = 12; 8.73 +/- 0.12, n = 8, respectively). In contrast the NK3 receptor-selective antagonist SB 223412 had a minimal effect on NKA responses and affinity values were low (pK(B) 5.81 +/- 0.11, n = 12 in normal; 5.75 +/- 0.08, n = 12 in idiopathic overactive, and 5.77 +/- 0.13, n = 11 in neurogenic overactive). CONCLUSION: These data indicate that NKA-induced responses are impaired in detrusor muscle from idiopathic overactive human bladder, but not in detrusor muscle from neurogenic overactive bladder. The NK2 receptor subtype appears to mediate NKA responses in the normal, idiopathic overactive, and neurogenic overactive detrusor. This is important evidence suggesting a difference between the bladder pathophysiology observed in idiopathic versus neurogenic overactive detrusor.

Benzamides↗

PubMed2005

Recent advances in basic science for overactive bladder.

PURPOSE OF REVIEW: Detrusor overactivity is a relatively common yet embarrassing symptom complex with significant impact on quality of life. The mainstay of current pharmacological treatment involves the use of muscarinic receptor antagonists, but their therapeutic effectiveness is limited by a combination of limited efficacy and troublesome side effects and has recently been challenged by Herbison et al. Recognition of the limitations of existing therapy has started the search for pharmacotherapeutic agents acting on alternative pathways underlying detrusor overactivity with the intention of improving storage symptoms of urgency, frequency and urge incontinence. RECENT FINDINGS: Recent research has suggested that several transmitters may modulate bladder storage. However, no agents currently available, acting via mechanisms other than muscarinic receptors have entered clinical practice so far. It is clear that far from being a passive container for urine, the urothelium is a crucial area within the bladder wall and its functions are complex and only now beginning to be appreciated. The release of several neurotransmitters from urothelium in response to distension and its action on receptors on sensory neurons is being increasingly recognized. The role for this afferent stimulation on the micturition reflex is gradually gaining importance in the pathophysiology of detrusor overactivity. SUMMARY: In this article, the recent developments in basic science related to the pathogenesis and pharmacological basis for future drug targets for effective management of overactive bladder are discussed.

Adenosine Triphosphate↗

PubMed2004

Influence of agonist intrinsic activity on the desensitisation of beta2-adrenoceptor-mediated responses in mast cells.

1. The aim of the present study was to determine whether the intrinsic activity of an agonist influences the extent of desensitisation of beta(2)-adrenoceptor-mediated responses in human lung mast cells. 2. The effects of a wide range of beta-adrenoceptor agonists (10(-10)-10(-5) m) on the IgE-mediated release of histamine from mast cells were determined. The intrinsic activity of agonists was established by comparing the maximal inhibitory response (E(max)) of an agonist relative to the maximal response obtained with the full agonist, isoprenaline. The intrinsic activity order for the inhibition of histamine release was isoprenaline (1.0)>formoterol (0.94)>fenoterol (0.89)>terbutaline (0.84)>salbutamol (0.69)>clenbuterol (0.65)>salmeterol (0.30)>dobutamine (0.20). 3. There was a significant (P<0.05) positive correlation (r=0.81) between the extent to which beta-adrenoceptor agonists inhibited histamine release and the degree to which the agonists caused elevations in cAMP in mast cells. 4. Further studies investigated the effects of long-term (24 h) incubation of mast cells with beta-adrenoceptor agonists on the subsequent ability of isoprenaline to inhibit histamine release. At concentrations of agonists selected to occupy a large percentage (88%) of beta(2)-adrenoceptors, there was a significant (P<0.05) correlation (r=0.73) between the relative intrinsic activity of agonists as inhibitors of histamine release and the extent of functional desensitisation induced by the agonists. At lower receptor occupancies, however, there was no correlation between the relative intrinsic activity of agonists and the extent of agonist-induced desensitisation. 5. These data indicate that, under experimental conditions where high receptor occupancies prevail, agonist intrinsic activity influences the extent of desensitisation of beta(2)-adrenoceptor-mediated responses in mast cells.

Adrenergic beta-2 Receptor Agonists↗

PubMed2004

Characteristics of adenosine triphosphate [corrected] release from porcine and human normal bladder.

PURPOSE: Although the sensory and motor roles of the purinergic system in the bladder are well proven in animal species, there is increasing evidence that it may have an important role in humans. In addition, it may be important in the pathophysiology of bladder dysfunction. We established the level of adenosine triphosphate (ATP) release from porcine and normal human bladders. MATERIALS AND METHODS: Bladder strips from patients with a urodynamically proven stable bladder undergoing surgery for stress incontinence and those undergoing cystectomy for cancer with no lower urinary tract symptoms were subjected to varying degrees of stretch (up to 50%) and electric field stimulation (10 to 40 Hz). A luciferase assay was used to quantify ATP release. RESULTS: Significantly increased ATP release over baseline was induced by mechanical and electrical stimulation (each p <0.05). Mean ATP release +/- SE from porcine bladders (38.2 +/- 1.9 pM/gm tissue following stretch and 19.9 +/- 6.5 pM/gm following electrical stimulation) was comparable to the release from human bladders (26.1 +/- 2.4 pM/gm tissue following stretch and 29.9 +/- 1.0 pM/gm following electrical stimulation). The main source of ATP release was the urothelium and not the muscle (p <0.05). This ATP release following stretch was not tetrodotoxin sensitive. CONCLUSIONS: The characteristics of ATP release from porcine and human bladders are similar and, therefore, the pig is a good model for humans. The main source of ATP release is urothelium from predominantly nonneuronal sources. This study supports a sensory role for ATP. An increased role for this purinergic neurotransmission may result in functional motor as well as sensory bladder disorders.

Adenosine Triphosphatases↗

PubMed2004

Potential therapeutic targets for the treatment of detrusor overactivity.

Current treatments for the overactive detrusor are poorly tolerated and can exert significant adverse effects. Possible targets for the development of new treatments are considered. Potential targets in four locations are examined: detrusor smooth muscle, urothelium, peripheral nerves and the CNS. In the detrusor, the role of various muscarinic receptor subtypes is discussed and beta-adrenoceptor agonists, phosphodiesterase inhibitors and potassium channel openers, all of which inhibit detrusor contractility, are considered for drug development. In the urothelium, a number of substances are released that affect bladder function including ATP, acetylcholine and an inhibitory factor that has yet to be identified. All three systems have the potential to be novel targets for drug development. Other possible therapeutic targets are the mechanisms influencing transmitter release in the bladder, for example, prejunctional 5-hydroxytryptamine (5-HT) 4 receptors. Finally, targets within the CNS and spinal cord are considered, including opioid receptors, 5-HT receptors and alpha-adrenoceptors.

Drug Delivery Systems↗

PubMed2004

Muscarinic receptor subtypes of the bladder and gastrointestinal tract.

The parasympathetic nervous system is responsible for maintaining normal intestinal and bladder function, contracting the smooth muscle by releasing the neurotransmitters acetylcholine (ACh) and ATP and relaxing sphincters by releasing nitric oxide. ACh is the main transmitter released and smooth muscle contraction is mediated via a mixed M2/M3 receptor population; M3 receptors acting via phospholipase C and M2 receptors acting via inhibition of adenylate cyclase. In ileal, colonic, gastric and bladder (detrusor) smooth muscle the density of M2 receptors is far greater than the density of M3 receptors, the M2:M3 ratio being 3:1 in most species including man. Despite the predominance of M2-receptors, direct contraction of intestinal and detrusor smooth muscle is mediated via the M3-receptor subtype and only this subtype is involved in contraction in vitro. Furthermore, knocking out the M3-receptor gene can have severe consequences on intestinal and bladder responses. In some tissues however M2-receptors may mediate an indirect "re-contraction" whereby a reduction in adenylate cyclase activity reverses the relaxation induced by beta-adrenoceptor stimulation. Thus, intestinal and bladder responses to muscarinic agonists are slightly depressed in M2 receptor knockout mice. The role of receptor subtypes in disease is unclear, but an enhancement of M2 receptor mediated responses has been reported to occur in diabetes. Animal models suggest that M2 receptors may play a greater role in some situations such as in the denervated bladder and intestine. In human disease the mechanisms operating are not so clear. Detrusor sensitivity to muscarinic agonists is enhanced in the neurogenic overactive bladder, but there is controversy surrounding the role of M2 receptors and conflicting results have been reported. Thus, the main muscarinic receptor mediating contraction in normal smooth muscle is the M3 receptor, but M2 receptors are also present and possibly may have an enhanced role in disease.

Animals↗

PubMed2003

Desensitisation of mast cell beta2-adrenoceptor-mediated responses by salmeterol and formoterol.

1. The long-acting beta(2)-adrenoceptor agonist formoterol (10(-10)-10(-6) m) inhibited the IgE-dependent release of histamine from human lung mast cells in a concentration-dependent manner. Formoterol was more potent and a full agonist relative to the nonselective beta-adrenoceptor agonist isoprenaline. By contrast, the long-acting beta(2)-adrenoceptor agonist salmeterol (10(-10)-10(-6) m) was about two-thirds less efficacious than either formoterol or isoprenaline as an inhibitor of histamine release. 2. Isoprenaline, formoterol and salmeterol (all at 10(-5) m) increased total cell cAMP levels in mast cells over basal by 361+/-90 (P<0.05), 321+/-89 (P<0.05) and 64+/-24% (P>0.05), respectively. 3. Long-term (24 h) incubation of mast cells with formoterol (10(-6) m) or salmeterol (10(-6) m) essentially abolished the subsequent ability of isoprenaline to inhibit histamine release. Both formoterol and salmeterol were more effective at inducing the functional desensitisation than isoprenaline (10(-6) m) or the short-acting beta(2)-adrenoceptor agonist salbutamol (10(-6) m). 4. The desensitisation induced by long-term treatments with salmeterol and formoterol was specific for beta(2)-adrenoceptor-mediated inhibition of histamine release as the inhibitory effects of alternative cAMP-elevating compounds, prostaglandin E(2), a receptor-mediated activator of adenylate cyclase, and forskolin, a direct activator of adenylate cyclase, were unaffected by desensitising treatments. 5. Radioligand binding studies were performed to determine beta(2)-adrenoceptor density in cell membranes after pretreatment (24 h) of cells with agonists. Isoprenaline, formoterol and salmeterol (all at 10(-6) m) reduced beta(2)-adrenoceptor density by 13+/-5 (P>0.05), 49+/-13 (P<0.05) and 35+/-17% (P>0.05), respectively. 6. These data indicate that long-term exposure of mast cells to both salmeterol and formoterol can cause substantial levels of desensitisation to beta(2)-adrenoceptor-mediated responses in mast cells.

Albuterol↗

PubMed2003

Potentiation of 5-hydroxytryptamine (5-HT) responses by a 5-HT uptake inhibitor in pulmonary and systemic vessels: effects of exposing rats to hypoxia.

The aim was to determine whether uptake of 5-hydroxytryptamine (5-HT) by the 5-HT transporter (SERT) modulates contractile responses to 5-HT in rat pulmonary arteries and whether this modulation is altered by exposure of rats to chronic hypoxia (10% oxygen; 8 h/day; 5 days). The effects of the SERT inhibitor, citalopram (100 nM), on contractions to 5-HT were determined in isolated ring preparations of pulmonary artery (intralobar and main) and compared with data obtained in systemic arteries. In intralobar pulmonary arteries citalopram produced a potentiation (viz. an increase in potency, pEC(50)) of 5-HT. The potentiation was endothelium-dependent in preparations from normoxic rats but endothelium-independent in preparations from hypoxic rats. In main pulmonary artery endothelium-independent potentiation was seen in preparations from hypoxic rats but no potentiation occurred in preparations from normoxic rats. In systemic arteries, citalopram caused endothelium-independent potentiation in aorta but no potentiation in mesenteric arteries; there were no differences between hypoxic and normoxic rats. It is concluded that SERT can influence the concentration of 5-HT in the vicinity of the vasoconstrictor receptors in pulmonary arteries. The data suggest that in pulmonary arteries from hypoxic rats, unlike normoxic rats, the SERT responsible for this effect is not in the endothelium and, hence, is probably in the smooth muscle. The data are compatible with reports that, in the pulmonary circulation, hypoxia induces/up-regulates SERT, and hence increases 5-HT uptake, in vascular smooth muscle. The findings may have implications in relation to the suggested use of SERT inhibitors in the treatment of pulmonary hypertension.

Animals↗

PubMed2003

Role of beta-adrenoceptor subtypes in mediating relaxation of the pig bladder trigonal muscle in vitro.

AIMS: To investigate the role of beta-adrenoceptor subtypes in mediating relaxation of the pig bladder trigonal muscle in vitro. MATERIALS AND METHODS: Longitudinal strips of trigonal muscle were isolated, and the mucosa and serosa removed. Tissues were precontracted with KCl, and beta-adrenoceptor agonists (isoprenaline or salbutamol) were added cumulatively, and concentration-relaxation curves (CRCs) were obtained. CRCs to agonists were obtained in the absence and presence of antagonists and antagonist affinity values were calculated. RESULTS: Isoprenaline (non-selective beta-agonist) relaxed with high potency (pEC(50) = 7.2). Propranolol antagonized CRCs to isoprenaline with a high affinity (apparent pK(B) = 8.8), but the Schild plot had a slope significantly (P < 0.01) less than unity (0.61), suggesting that responses were mediated by more than one beta-adrenoceptor subtype. CGP20712A (beta(1)-antagonist) antagonized responses to isoprenaline with a low affinity (apparent pK(B) = 5.13), indicating beta(1)-adrenoceptors did not participate in the response. The affinity of ICI118551 (beta(2)-antagonist) for antagonism of responses to isoprenaline was also relatively low (apparent pK(B) = 6.9), and the Schild slopes were significantly (P < 0.01) less than unity (0.58). SR59230A (beta(3)-antagonist) antagonized CRCs to isoprenaline with a relatively low affinity (apparent pK(B) = 7.5), and with a Schild slope significantly (P < 0.01) less than unity (0.86), indicating that responses may be mediated by more than one beta-adrenoceptor subtype. In contrast to that observed with isoprenaline, the beta(2)-adrenoceptor selective agonist salbutamol induced relaxation with a relatively low potency (pEC(50) = 6.6) and with maximum responses of 80% of that to isoprenaline. ICI118551 competitively antagonized (Schild plot of unity) responses to salbutamol with a high affinity (pA2 = 8.3). CONCLUSIONS: These data suggest that beta-adrenoceptor mediated responses to isoprenaline of the bladder trigone are mediated via both the beta(2)- and beta(3)-adrenoceptor subtypes whilst responses to salbutamol appear to be mediated only via the beta(2)-adrenoceptor.

Adrenergic beta-Agonists↗

PubMed2003

Desensitization of beta2-adrenoceptor-mediated responses by short-acting beta2-adrenoceptor agonists in human lung mast cells.

1 The principal aim of the present study was to determine whether long-term treatment of human lung mast cells (HLMC) with the clinically-relevant beta(2)-adrenoceptor agonists, salbutamol and terbutaline, leads to desensitization of beta(2)-adrenoceptor-mediated responses in these cells. 2 The non-selective beta-adrenoceptor agonist, isoprenaline, and the selective beta(2)-adrenoceptor agonists, salbutamol and terbutaline, inhibited the IgE-mediated release of histamine from HLMC. Salbutamol (pD(2); 7.7+/-0.3) and terbutaline (pD(2); 7.3+/-0.2) were roughly equipotent as inhibitors of histamine release although both agonists were less potent than isoprenaline (pD(2); 8.6+/-0.2). 3 Isoprenaline (10(-5) M), salbutamol (10(-5) M) and terbutaline (10(-5) M) enhanced total cell cAMP levels in HLMC over basal by 361+/-90, 150+/-38 and 165+/-35%, respectively. 4 Long-term exposure (24 h) of HLMC to either salbutamol (10(-7) M) or terbutaline (10(-7) M) led to a subsequent reduction in the effectiveness of salbutamol and terbutaline (both 10(-9)-10(-4) M) to inhibit histamine release. However, salbutamol was significantly (P<0.05) more effective than terbutaline at promoting the functional desensitization. 5 Radioligand binding studies, using iodinated cyanopindolol, were performed to determine beta(2)-adrenoceptor density in cell membranes after pretreatment (24 h) of cells with either salbutamol (10(-6) M) or terbutaline (10(-6) M). Both agonists reduced beta(2)-adrenoceptor density in membranes to about the same extent (approximately 25% reduction) but these changes in receptor density were not statistically significant (P>0.05). 6 These data indicate that long-term exposure of mast cells to salbutamol causes greater levels of desensitization to beta(2)-adrenoceptor-mediated responses in HLMC than terbutaline. These findings may have wider clinical significance in the context of asthma treatment as compromised mast cell inhibition could result following long-term exposure of mast cells to short-acting bronchodilators.

Adrenergic beta-Agonists↗

PubMed2003

Recent developments in the management of detrusor overactivity.

PURPOSE OF REVIEW: Detrusor overactivity is a relatively common yet embarrassing symptom complex with significant impact on quality of life. The mainstay of current pharmacological treatment involves use of muscarinic receptor antagonists, but their therapeutic efficacy is limited by their troublesome side effects resulting in the non-continuance of treatment in a significant number of patients. Therefore, the development of new drugs can proceed by targeting alternative pathways affecting detrusor overactivity. In this article, the pharmacological basis for the current therapeutic alternatives for managing detrusor overactivity and possible future developments are discussed. RECENT FINDINGS: It is clear that far from being a passive container for urine, the urothelium is a crucial part of the bladder. Its functions are complex, dynamic and important, and only now becoming understood. The release of ATP from urothelium in response to distension and its action on P2X receptors resulting in activating both motor and sensory neurons is being increasingly recognised. In the normal bladder, muscarinic receptor stimulation produces the main part of detrusor contraction. However, in functionally abnormal bladders, a non-cholinergic activation via the purinergic receptors may occur. The central nervous mechanisms controlling the micturition reflex have also recently attracted attention. SUMMARY: Recent research has suggested that several transmitters may modulate voiding. However, few drugs with clinical benefits have been developed so far. Present treatments for overactive bladders have significant non-compliance rates. Hopefully, future research will lead to drugs with greater therapeutic benefits and better tolerance.

Adrenergic beta-Agonists↗

PubMed2003

The functional role of beta-adrenoceptor subtypes in mediating relaxation of pig urethral smooth muscle.

PURPOSE: The predominant beta-adrenoceptor subtype present in the bladder and urethra is beta3-adrenoceptors. We investigated the role of beta-adrenoceptors in mediating relaxation of the in vitro female pig urethra. MATERIALS AND METHODS: Circular strips of urethral tissues were pre-contracted with KCl. Concentration-relaxation curves (CRCs) to beta-adrenoceptor agonists were obtained in the absence and presence of antagonists. RESULTS: The nonselective beta-agonist isoproterenol in 30 animals and the beta3-adrenoceptor agonist BRL37344 in 4 relaxed with high potency (pEC50 7.2 and 8.1, respectively), while the beta2-adrenoceptor agonist salbutamol in 6 had low potency (pEC50 6.1). Mean maximal relaxation responses of BRL37344 and salbutamol relative to maximal isoproterenol responses were 89.8% and 76.7%, respectively. Propranolol (10 to 100 nM) in 18 animals antagonized CRCs to isoproterenol with high affinity (apparent pKB 8.6) but the Schild plot had a slope that was significantly less than unity (0.68, p <0.01). High concentrations of the beta1-antagonist CGP20712A (3 to 30 microM) in 12 animals had no effect on responses to isoproterenol. The beta2-antagonist ICI118551 (30 to 300 nM) in 25 animals antagonized responses to isoproterenol with high affinity (apparent pKB 8.03) with a Schild slope not different from unity (0.79). The beta3-antagonist SR59230A (10 to 100 nM) in 12 animals antagonized CRCs to isoproterenol with an apparent pKB of 7 and with a Schild slope that was again significantly less than unity (0.62, p <0.01), indicating that responses to isoproterenol are mediated by more than 1 beta-adrenoceptor subtype. According to the Schild plot of unity ICI118551 (3 to 30 nM) in 18 animals competitively antagonized responses to salbutamol with high affinity (pA2 8.5). CONCLUSIONS: In the pig urethra beta-adrenoceptor mediated relaxations to isoproterenol are mediated via beta2 and beta3-adrenoceptors, while responses to beta2-adrenoceptor agonists such as salbutamol appear to be mediated only via beta2-adrenoceptors.

Adrenergic beta-Agonists↗

PubMed2002

Pharmacological characterisation of the beta-adrenoceptor expressed by human lung mast cells.

The nonselective beta-adrenoceptor agonist, isoprenaline (pD2; 8.8 +/- 0.2), and selective beta2-adrenoceptor agonists, clenbuterol (9.2 +/- 0.4) and salbutamol (7.1 +/- 0.1), inhibited the immunoglobulin E-mediated release of histamine from human lung mast cells in a concentration-dependent manner. The beta2-adrenoceptor-selective antagonist, ICI118551 (erythro-(+/- )-1-(7-methylindan-4-yloyl)-3-isopropylaminobutan-2-ol HCl), antagonised the isoprenaline inhibition of histamine release from human lung mast cells with high affinity (apparent pK(B); 9.5 +/- 0.2), whereas high concentrations of the beta1-adrenoceptor-selective antagonist, CGP20712A (2-hydroxy-5-(2-(hydroxy-3-(4((1-methyl-4-trifluoromethyl)-1-H-imidazol-2-yl)-phenoxy)-propyl)-aminoethoxyl)-benzamide), were required to reverse the isoprenaline inhibition (apparent pK(B); 6.5 +/- 0.3). Radioligand binding studies using [125I]-iodocyanopindolol ([125I]CYP) were performed on membranes derived from purified mast cells (>90% purity). Binding of [125I]CYP to mast cell membranes was displaced from a single binding site with a high affinity for ICI118551 (pK(i); 8.9 +/- 0.1) and low affinity for CGP20712A (pK(i); 6.0 +/- 0.03), indicative of a homogeneous population of beta2-adrenoceptors. In contrast, in human lung membranes, these antagonists displaced [125I]CYP from two sites indicative of a heterogeneous population of beta1-adrenoceptors (20%) and beta2-adrenoceptors (80%). These data indicate that the beta-adrenoceptor expressed by human lung mast cells and mediating inhibition of mediator release from these cells is the beta2-adrenoceptor.

Adrenergic beta-Agonists↗

PubMed2002

Identification of beta-adrenoceptor subtypes in lower urinary tract of the female pig.

PURPOSE: We investigated the presence and functional role of beta-adrenoceptor subtypes in the bladder base and proximal urethra of the female pig. MATERIALS AND METHODS: Saturation experiments were done with 7 concentrations (0.25 to 16 nM.) of [(3)H]-dihydroalprenolol (NEN Life Science Products, Boston, Massachusetts). Competition experiments with [(3)H]-dihydroalprenolol were performed with unlabeled antagonists (beta1 selective CGP20712A, beta2 selective ICI118551 and beta3 selective SR59230A). In functional studies concentration-relaxation curves to the beta3-agonist BRL37344 were obtained and antagonist affinities for SR59230A were determined. RESULTS: CGP20712A displaced [(3)H]-dihydroalprenolol with low affinity, suggesting that beta1-adrenoceptors were not present. Displacement with ICI118551 in the bladder base and urethra best fitted a 2-site model with 20% and 28% high affinity sites (beta2), respectively. Displacement experiments with SR59230A in the bladder base demonstrated that 59% of binding sites had high affinity (beta3). In the urethra displacement with SR59230A best fitted a 1-site model but with a pK(i) of 7.2 that was intermediate between that expected for beta2 and beta3-adrenoceptors. In functional studies BRL37344 induced relaxation with pEC50 values of 5.5 and 8, and a maximum relaxation response relative to 30 microM. isoprenaline of 79% and 90% in the bladder base and urethra, respectively. The affinity value of SR59230A for the response to BRL37344 was 7.87 and 7.71 in the bladder base and urethra, respectively, which were intermediate between those of beta2 and beta3-adrenoceptors. CONCLUSIONS: Apparently beta3-adrenoceptors are the predominant beta-adrenoceptor subtype present in the lower urinary tract of the pig.

Adrenergic beta-Agonists↗

PubMed2002

Muscarinic receptor subtypes and management of the overactive bladder.

Anticholinergic agents are the most widely used therapy for urge incontinence despite exerting adverse effects, such as constipation, tachycardia, and dry mouth, that limit their use. These adverse effects result from a lack of selectivity for the bladder over other organs. Although M2-muscarinic receptors are the predominant cholinoreceptor present in urinary bladder, the smaller population of M3-receptors appears to be the most functionally important and mediates direct contraction of the detrusor muscle. M2-receptors modulate detrusor contraction by several mechanisms and may contribute more to contraction of the bladder in pathologic states, such as bladder denervation or spinal cord injury. Prejunctional inhibitory M2-receptors or M4-receptors and prejunctional facilitatory M1-muscarinic receptors in the bladder have also been reported, but their relevance to the clinical effectiveness of muscarinic antagonists is unknown. In clinical studies, tolterodine, a nonselective muscarinic antagonist, has been reported to be equally effective to oxybutynin but to induce less dry mouth. Controlled-release and intravesical, intravaginal, and rectal administrations of oxybutynin have all been reported to cause fewer adverse effects. Conversely, darifenacin, a new M3-selective antagonist, has been reported to have selectivity for the bladder over the salivary gland in vivo. Whether M3-selective or nonselective muscarinic antagonists will be the most clinically effective for the overactive bladder-preserving the best balance between efficacy and tolerability-has yet to be established, and comparative clinical trials between compounds, such as darifenacin (M3 selective) and tolterodine (nonselective) will be required.

Cholinergic Antagonists↗

PubMed2002

The role of beta(3)-adrenoceptors in mediating relaxation of porcine detrusor muscle.

1. beta-adrenoceptors mediate relaxation of bladder detrusor smooth muscle. This study investigates the contribution of beta(3)-adrenoceptors to relaxation of the pig urinary bladder. 2. Cell membranes were prepared from detrusor muscle of the pig bladder dome and competition experiments with [(3)H]-dihydroalprenolol (DHA), a non-selective beta-adrenoceptor antagonist was used as a specific radioligand to determine the presence of beta-adrenoceptor subtypes. In functional experiments, isolated detrusor muscle strips were used to determine the potency of agonists and the affinity of antagonists. 3. In competition binding experiments, CGP20712A (beta(1)-adrenoceptor selective) displaced [(3)H]-DHA from a single binding site with a low affinity. In contrast, displacement data for ICI 118551 (beta(2)-adrenoceptor antagonist) and SR59230A (beta(3)-adrenoceptor antagonist) best fitted a two-site model suggesting a predominant (70%) population of beta(3)-adrenoceptors. 4. In functional studies, isoprenaline and salbutamol (beta(2)-adrenoceptor agonist) relaxed KCl precontracted muscle strips with high potency (pEC(50) 7.7 and 7.2, respectively), whilst CGP12177 and BRL37344 (beta(3)-adrenoceptor agonists) had low potency and were partial agonists. CGP20712A and atenolol (beta(1)-adrenoceptor antagonists) antagonised responses with a low affinity. ICI118551 antagonized responses to isoprenaline and salbutamol with a high affinity (pK(B)=7.8 and 8.7, respectively), but the Schild slopes were low suggesting that responses were mediated by more than one beta-adrenoceptor. The Schild plot for SR59230A was biphasic, apparent pK(B) values for 3 - 10 nM SR59230A being 8.6 and those for 30 nM - 1 microM being 7.7. 5. These data suggest that beta(3)-adrenoceptors are the predominant beta-adrenoceptor subtype present in the pig bladder and that beta-adrenoceptor mediated responses of this tissue are mediated via both the beta(2)- and beta(3)-adrenoceptor subtypes.

Adrenergic beta-Agonists↗

PubMed2002

The use of alpha-adrenoceptor antagonists in lower urinary tract disease.

alpha-adrenoceptor antagonists have traditionally been used in the treatment of hypertension but in recent years they have become increasingly common in the treatment of benign prostatic enlargement (BPE), where they reduce the 'dynamic' component of bladder outlet obstruction and appear to have additional actions to reduce irritative symptoms of the disease. Prazosin (Hypovase), Alza), doxazosin (Cardura), Pfizer), indoramin (Doralese), Wyeth-Ayerst Pharmaceuticals Inc.) and terazosin (Hytrin), Abbott Laboratories) are currently available in the UK for BPE but these agents have cardiovascular actions in a significant number of patients, inducing effects which must be considered adverse unless the patient also requires treatment for mild-to-moderate hypertension. The uroselective alpha-adrenoceptor antagonists tamsulosin (Flomax), Yamanouchi Pharmaceutical Co. Ltd.) and alfuzosin (Xatral), Sanofi-Synthelabo) have recently been introduced. These agents exert their selectivity via different mechanisms; selective tissue distribution for alfuzosin and alpha-adrenoceptor subtype selectivity for tamsulosin. The incidence of cardiovascular side effects for both drugs is similar to placebo. Several lines of evidence suggest that the alpha-adrenoceptor antagonists may relieve lower urinary tract (LUT) symptoms by other mechanisms additional to those which account for the reduction in bladder outlet obstruction. If correct, these agents may be of use in the treatment of other bladder conditions.

Adrenergic alpha-Antagonists↗

PubMed2002

The role of M2 muscarinic receptor subtypes in mediating contraction of the pig bladder base after cyclic adenosine monophosphate elevation and/or selective M3 inactivation.

PURPOSE: In the bladder body M2 muscarinic receptors predominate but a smaller population of M3 receptors mediates direct detrusor contraction. M2 receptors have an indirect role by inhibiting cyclic adenosine monophosphate mediated relaxation in the bladder body. We investigated whether a similar mechanism also exists in the bladder base. METHODS: Experiments were performed on pig detrusor muscle. In receptor binding studies using l-quinuclidinyl [phenyl-4-(3)H] benzilate ([(3)H]QNB) (NEN Life Science Products, Inc., Boston, Massachusetts) displacement experiments were performed with subtype selective antagonists to determine the M2-to-M3 receptor ratio. In functional studies the affinity of these antagonists against carbachol induced contractions was calculated in normal tissues and in tissues after cyclic adenosine monophosphate elevation by pre-contraction with KCl and relaxation with isoprenaline, and/or selective M3 inactivation by incubation with 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP) mustard (Sigma Chemical Co., St. Louis, Missouri) in the presence of methoctramine (Sigma Chemical Co.) to protect M2 receptors. RESULTS: In saturation binding studies receptor density was 130.5 of fmol./mg. protein and the dissociation constant for [(3)H]QNB was 0.27 nM. Displacement of [(3)H]QNB by the M3 selective antagonist 4-DAMP and the M2 antagonist methoctramine indicated an M2-to-M3 ratio of about 3:1. In functional studies 4-DAMP and methoctramine caused competitive antagonism of responses with affinity values of 9.5 and 6.3 in normal tissues, and 9.3 and 6.1, respectively, in cyclic adenosine monophosphate elevated tissues, suggesting the involvement of M3 receptors only. In tissues in which M3 receptors were inactivated and cyclic adenosine monophosphate levels were elevated the affinity of 4-DAMP was significantly reduced to 8.5 but that of methoctramine was significantly increased to 6.5, suggesting the involvement of M2 receptors. CONCLUSIONS: The M3 subtype appears to mediate contraction of the normal and cyclic adenosine monophosphate elevated tissues of the bladder base. Involvement of M2 receptors was only noted after selective M3 inactivation and cyclic adenosine monophosphate elevation.

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