Biomedical subjects

E H Ohlstein

Publications and source records attributed to E H Ohlstein.

At least 37 records · Page 2Linked to original sources

PubMed2000

Expression of monocyte chemotactic protein-3 mRNA in rat vascular smooth muscle cells and in carotid artery after balloon angioplasty.

Monocyte chemotactic protein-3 (MCP-3) is a CC chemokine that functions in chemoattraction and activation of monocytes, T lymphocytes, eosinophils, basophils, natural killer cells and dendritic cells. The activation of the target cells by MCP-3 is via specific chemokine receptors CCR2 and CCR3, of which CCR2 is shared with MCP-1. MCP-1 and CCR2 have been implicated in vascular diseases including atherosclerosis and restenosis, that are known to be involved in inflammation (accumulation of T lymphocytes and monocytes) and smooth muscle cell (SMC) activation (proliferation, migration and matrix deposition). To investigate a potential role of MCP-3 in vascular injury, the present work examined its mRNA expression in rat aortic SMCs stimulated with various inflammatory stimuli including LPS, TNF-alpha, IL-1beta, IFN-gamma and TGF-beta. A time- and concentration-dependant induction of MCP-3 mRNA in SMCs was observed by means of Northern analysis. A strikingly similar expression profile was observed for MCP-3 and MCP-1 mRNA in SMCs. Furthermore, MCP-3 mRNA expression was induced in rat carotid artery after balloon angioplasty. A significant induction in MCP-3 mRNA was observed in the carotid artery at 6 h (41-fold increase over control, P<0.001), 1 day (13-fold increase, P<0.001) and 3 days (6-fold increase, P<0.01) after balloon angioplasty as quantitated by reverse transcription and polymerase chain reaction. These data provide evidence for the cytokine-induced expression of MCP-3 in SMCs and in carotid artery after balloon angioplasty, suggesting a potential role of MCP-3 in the pathogenesis of restenosis and atherosclerosis.

Angioplasty, Balloon↗

PubMed2000

Application of in vivo and ex vivo magnetic resonance imaging for evaluation of tranilast on neointima formation following balloon angioplasty of the rat carotid artery.

OBJECTIVE: Recent studies suggest that tranilast inhibits a variety of agents implicated in neointimal growth and restenosis in experimental animal models and humans. We report here a study evaluating the efficacy of tranilast in the rat carotid artery balloon angioplasty model, a model that mimics many aspects of the percutaneous transluminal angioplasty procedure in humans. Efficacy was determined based on in vivo and ex vivo magnetic resonance imaging (MRI) as well as by histomorphometry. The utility of this study, using a reverse paradigm, is to investigate if agents successful in the clinic can demonstrate efficacy in this animal model primary screen as measured by MRI and histomorphometry. METHODS: Tranilast (300 mg/kg/day, p.o.) was administered to Sprague-Dawley rats 3 days prior to balloon injury and continued for 14 days after injury. Three methods of measuring the vascular injury that occurs in this model were employed: (1) in vivo MRI, used to measure in vivo lumen volumes for the carotid artery once at baseline (pre-surgery) and again at 14 days post angioplasty; (2) ex vivo MRI (and histomorphometry), used to evaluate the total arterial wall thickness and the intima-to-media ratio; and (3) analysis of collagen density, used to evaluate the efficacy of tranilast to abrogate collagen synthesis and deposition following vascular injury. RESULTS: Tranilast provided 33% protection (P<0.05) from angioplasty-induced lumen narrowing as measured by MRI in vivo. The results of the ex vivo MR analysis of total wall thickness showed a 14% protection of angioplasty-induced narrowing (P<0.05), and the mean intima-to-media ratio showed a 39% (P<0.006) protection for the tranilast-treated rats. Histological analysis of the mean intima-to-media ratio demonstrated that tranilast provided 36% (P<0. 01) protection in the intima-to-media ratio. Further, treatment with tranilast showed a 52% reduction in collagen density of the intimal layer and a 70% reduction in collagen density of the medial layer of the injured arteries. CONCLUSION: The data obtained by in vivo MRI, ex vivo MRI, histology and collagen analysis demonstrate that tranilast provided significant beneficial effects in inhibiting neointimal formation in the rat carotid artery model. Also this study, to the best of our knowledge, is the first to harness complimentary information from various technologies, including lumen patency by in vivo MRI, neointimal formation by ex vivo MRI and conventional histomorphometry, and histological analysis for collagen density, to provide a comprehensive understanding of the pathology in this disease model.

Analysis of Variance↗

PubMed2000

Human urotensin-II, the most potent mammalian vasoconstrictor identified to date, as a therapeutic target for the management of cardiovascular disease.

The novel cyclic undecapeptide human urotensin-II (hU-II) and its high-affinity G-protein-coupled receptor, GPR14, are both expressed within the human cardiovasculature (vascular smooth muscle, endothelium, myocardium, coronary atheroma, etc.) and may, therefore, contribute to the (patho)physiological regulation of cardiovascular homeostasis in humans. Indeed, hU-II is an efficacious, sustained spasmogen of mammalian isolated blood vessels including those from rats, rabbits, dogs, pigs, non-human primates and humans (where it is one to two orders of magnitude more potent than endothelin(ET)-1). In vivo, hU-II markedly alters systemic hemodynamics in the anesthetized primate (increase cardiac contractility [dP/dt], increase stroke volume, decrease total peripheral resistance) ultimately resulting in fatal cardiovascular collapse. As such, the development of selective hU-II receptor antagonists may be of utility in the management of cardiovascular disorders characterized by aberrant vasoconstriction, myocardial dysfunction and/or cardiac remodeling (e.g., myocardial infarction, congestive heart failure).

Animals↗

PubMed2000

Contractile responses to human urotensin-II in rat and human pulmonary arteries: effect of endothelial factors and chronic hypoxia in the rat.

Responses to human urotensin-II (hU-II) were investigated in human and rat pulmonary arteries. Rat pulmonary arteries: hU-II was a potent vasoconstrictor of main pulmonary arteries (2 - 3 mm i.d.) (pEC(50), 8.55+/-0.08, n=21) and was approximately 4 fold more potent than endothelin-1 [ET-1] (P<0.01), although its E(max) was considerably less (approximately 2.5 fold, P<0.001). The potency of hU-II increased 2.5 fold with endothelium removal (P<0.05) and after raising vascular tone with ET-1 (P<0.01). E(max) was enhanced approximately 1.5 fold in the presence of N(omega)-nitro-L-arginine methylester (L-NAME, 100 microM, P<0.01) and approximately 2 fold in vessels from pulmonary hypertensive rats exposed to 2 weeks chronic hypoxia (P<0.05). hU-II did not constrict smaller pulmonary arteries. Human pulmonary arteries ( approximately 250 microm i.d.): in the presence of L-NAME, 3 out of 10 vessels contracted to hU-II and this contraction was highly variable. hU-II is, therefore, a potent vasoconstrictor of rat main pulmonary arteries and this response is increased by endothelial factors, vascular tone and onset of pulmonary hypertension. Inhibition of nitric oxide synthase uncovers contractile responses to hU-II in human pulmonary arteries.

Animals↗

PubMed2000

Differential vasoconstrictor activity of human urotensin-II in vascular tissue isolated from the rat, mouse, dog, pig, marmoset and cynomolgus monkey.

1. Urotensin-II (U-II) and its G-protein-coupled receptor, GPR14, are expressed within mammalian cardiac and peripheral vascular tissue and, as such, may regulate mammalian cardiovascular function. The present study details the vasoconstrictor profile of this cyclic undecapeptide in different vascular tissues isolated from a diverse range of mammalian species (rats, mice, dogs, pigs, marmosets and cynomolgus monkeys). 2. The vasoconstrictor activity of human U-II was dependent upon the anatomical origin of the vessel studied and the species from which it was isolated. In the rat, constrictor responses were most pronounced in thoracic aortae and carotid arteries: -log[EC(50)]s 9.09+/-0.19 and 8.84+/-0.21, R(max)s 143+/-21 and 67+/-26% 60 mM KCl, respectively (compared, for example, to -log[EC(50)] 7.90+/-0.11 and R(max) 142+/-12% 60 mM KCl for endothelin-1 [ET-1] in thoracic aortae). Responses were, however, absent in mice aortae (-log[EC(50)] <6.50). These findings were further contrasted by the observation that U-II was a 'coronary-selective' spasmogen in the dog (-log[EC(50)] 9.46+/-0.11, R(max) 109+/-23% 60 mM KCl in LCX coronary artery), yet exhibited a broad spectrum of vasoconstrictor activity in arterial tissue from Old World monkeys (-log[EC(50)]s range from 8.96+/-0.15 to 9.92+/-0.13, R(max)s from 43+/-16 to 527+/-135% 60 mM KCl). Interestingly, significant differences in reproducibility and vasoconstrictor efficacy were seen in tissue from pigs and New World primates (vessels which responded to noradrenaline, phenylephrine, KCl or ET-1 consistently). 3. Thus, human U-II is a potent, efficacious vasoconstrictor of a variety of mammalian vascular tissues. Although significant species/anatomical variations exist, the data support the hypothesis that U-II influences the physiological regulation of mammalian cardiovascular function.

Animals↗

PubMed2000

Platelet agonist F11 receptor is a member of the immunoglobulin superfamily and identical with junctional adhesion molecule (JAM): regulation of expression in human endothelial cells and macrophages.

The stimulatory mAb F11 binds two platelet membrane proteins of 32 and 35 kDa and causes activation of platelets when cross-linked with the FcgammaRII receptor. We used bioinformatics to identify expressed sequence tags from libraries of cytokine-stimulated human endothelial cell (EC) cDNAs. The protein sequence deduced from full-length F11 cDNA was identical to partial sequences of peptides derived from affinity-purified platelet F11 antigen. F11 mRNA is expressed in human EC, macrophages, and a variety of non-hematopoietic vascular tissues. Expression of F11 mRNA is modulated by cytokines in EC and is up-regulated by oxidized low-density lipoprotein in human macrophages. The F11 receptor contains two immunoglobulin-like domains in its 236-amino-acid-long extracellular region, and has identity to the recently described junctional adhesion molecule. The data indicate that the F11 antigen is a novel receptor or cell adhesion molecule belonging to the immunoglobulin superfamily.

Amino Acid Sequence↗

PubMed2000

A comparison of carvedilol and metoprolol antioxidant activities in vitro.

Carvedilol is a vasodilating beta-blocker and antioxidant approved for treatment of mild to moderate hypertension. angina, and congestive heart failure. Metoprolol is a beta1-selective adrenoceptor antagonist. When carvedilol and metoprolol were recently compared in clinical trials for heart failure, each showed beneficial beta-blocker effects such as improved symptoms, quality of life, exercise tolerance, and ejection fraction, with no between-group differences. When thiobarbituric acid reactive substance (TBARS) levels were measured in serum as an indirect marker of free radical activity, there were also no between-group differences. However, we had noted superior cardioprotection by carvedilol in comparison to metoprolol in ischemia and reperfusion models. We therefore examined antioxidant activity directly in cells and tissues. Here we show that in cultured rat cerebellar neurons, and in brain and heart membranes, carvedilol has far greater antioxidant activity than metoprolol, which is essentially inactive as an antioxidant in these model systems. The antioxidant activity of carvedilol could be explained by a greater degree of lipophilicity, as measured by its ClogP value of 3.841 as contrasted to a ClogP value of 1.346 for metoprolol. Alternatively, the molecular structure of carvedilol favors redox recycling, which the structure of metoprolol does not. Therefore, carvedilol could have additional pharmacologic effects that are favorable for long-term therapy.

Adrenergic beta-Antagonists↗

PubMed2000

Targeted disruption of the endothelin-B-receptor gene attenuates inflammatory nociception and cutaneous inflammation in mice.

Endothelin-1 (ET-1) has been suggested to have a potential function as an inflammatory mediator. The study reported here assessed the putative inflammatory/nociceptive actions of the ET isopeptides using endothelin-B (ET(B))-receptor knockout (KO) mice and ET(A)- (SB 234551) and ET(B)- (A192621) selective antagonists. Phenylbenzoquinone (PBQ)-induced algesia was evident in the wild-type (WT) ET(B) (+/+) mice, attenuated by 80% in the heterozygous ET(B) (+/-) mice, and absent in the ET(B) (-/-) homozygotes. This was reproduced pharmacologically in WT ET(B) (+/+) mice where the algesic effect of PBQ was inhibited 74% by A192621, but unaffected by SB 234551 (both at 25 mg/kg p.o.). Similar observations were made in a model of cutaneous inflammation: ET(B) (+/+) mice had a marked inflammatory response to topical arachidonic acid, ET(B) (+/-) and ET(B) (-/-) mice had significantly reduced edema responses (37% and 65% inhibition). Neutrophil infiltration was reduced in the ET(B) (+/-) and ET(B) (-/-) mice (51% and 65% reduction, respectively). Topical administration of A192621 (500 microg/ear) inhibited arachidonic acid-induced swelling (39%) in WT ET(B) (+/+) mice. Collectively, these results support a role for the ET(B)-receptor in the mediation of inflammatory pain and cutaneous inflammatory responses. As such, the development of ET(B)-receptor-selective antagonists may be of therapeutic utility in the treatment of inflammatory disorders.

Animals↗

PubMed2000

Human urotensin-II is a potent vasoactive peptide: pharmacological characterization in the rat, mouse, dog and primate.

The observation that the novel G-protein-coupled receptor (GPCR) GPR14 and its cognate ligand, urotensin-II (U-II), are expressed within the mammalian vasculature raises the possibility that they may influence cardiohemodynamic homeostasis. To this end, this study examined the vasoactive properties of U-II in rodents, dogs and primates. In vitro, human U-II was a sustained vasoconstrictor with a potency (pD2s < or = 9) approximately an order of magnitude greater than that seen with endothelin-1 (ET-1), making it one of the most, if not the most, potent mammalian vasoconstrictor identified to date. However, in vitro responses exhibited significant anatomical and/or species-dependency, that is, human U-II was a selective 'aorto-coronary' vasoconstrictor in rats and dogs, inactive in mice and contracted all primate arteries studied. In vivo, this peptide evoked a complex, dose-dependent hemodynamic response in the anesthetized primate, culminating in severe myocardial depression and fatal circulatory collapse. As such, U-II may represent a novel neurohumoral regulator of mammalian cardiovascular physiology and pathology in particular disorders characterized by aberrant vascular smooth muscle and/or myocardial function.

Animals↗

PubMed2000

Selective antagonism of endothelin-A-receptors improves outcome in both head trauma and focal stroke in rat.

Increased levels of endothelin (ET) have been demonstrated in the ischemic brain, and ET receptor antagonism has been shown to improve outcome in cerebral ischemia. However, no previous work has been carried out evaluating the role of ET and its antagonism in brain trauma as compared to experimental stroke. In this study, we evaluated changes in brain ET levels following closed head injury (CHI) and the effects of SB 234551, an endothelin-A- (ET(A)) selective antagonist, and SB 209670, a mixed endothelin-A- and -B- (ET(A)/ET(B)) antagonist, on outcome in CHI and focal stroke. Male Sabra rats were subjected to CHI (weight drop model). Male Sprague Dawley rats were subjected to focal stroke (intraluminal suture model). Motor function(s) were assessed and immunoreactive ET (irET) and the degree of cerebral edema were measured for 24 h after CHI. Brain swelling (edema), neurological deficits and forebrain infarct volumes were measured 24 h after focal stroke. Antagonists (total doses of 7.5, 15, 30 or 60 mg/kg) were administered intravenously for 6-24 h (beginning 15 min after injury). Control rats were infused with vehicle. CHI resulted in increased ET levels in the directly contused hemisphere at 12 and 24 h. In addition, SB 234551 significantly reduced neurological deficits (decreased 30%) and brain edema (decreased 40%) following CHI (p < 0.05 at 60 mg/kg dose). SB 209670 had no effects on CHI outcome. Focal stroke studies yielded similar results. SB 234551 reduced focal stroke-induced neurological deficits by 50%, brain swelling by 54% and the degree of infarction by 36% (p < 0.05 at 30 mg/kg). SB 209670 did not provide any neuroprotection in focal stroke. These data indicate that ET plays a significant role in the pathophysiology of CHI, and that selectively targeting ET(A)-receptors similarly in both CHI and stroke might be a therapeutic opportunity.

Animals↗

PubMed2000

Drug discovery in the next millennium.

Selection and validation of novel molecular targets have become of paramount importance in light of the plethora of new potential therapeutic drug targets that have emerged from human gene sequencing. In response to this revolution within the pharmaceutical industry, the development of high-throughput methods in both biology and chemistry has been necessitated. This review addresses these technological advances as well as several new areas that have been created by necessity to deal with this new paradigm, such as bioinformatics, cheminformatics, and functional genomics. With many of these key components of future drug discovery now in place, it is possible to map out a critical path for this process that will be used into the new millennium.

Animals↗

PubMed2000

Nitric oxide stimulatory and endothelial protective effects of idoxifene, a selective estrogen receptor modulator, in the splanchnic artery of the ovariectomized rat.

Estrogen is known to stimulate endothelial nitric oxide production and attenuate endothelial dysfunction after ischemia and reperfusion. However, estrogen therapy increases the risk of breast and endometrial cancer. The present study was designed to determine whether idoxifene, a selective estrogen receptor modulator without adverse effects on reproductive organs, may stimulate nitric oxide release and protect endothelial function. In U-46619 precontracted superior mesenteric arterial (SMA) segments isolated from ovariectomized rats, idoxifene and 17 beta-estradiol resulted in a comparable dose-dependent vasorelaxation (maximal relaxation: 75.3 +/- 4.9 and 71 +/- 4.7%, respectively). Treatment of the rings with N(omega)-nitro-L-arginine methyl ester completely blocked idoxifene- and 17 beta-estradiol-induced vasorelaxation. In vitro incubation of SMA rings with TNF alpha significantly reduced vasorelaxation to an endothelium-dependent vasodilator, acetylcholine (maximal relaxation: 73 +/- 3.7 versus 95 +/- 2.9% pre-TNF alpha, P <.01). Idoxifene, but surprisingly not 17 beta-estradiol, prevented TNF alpha-induced endothelial dysfunction (maximal relaxation: 86 +/- 2.6% in idoxifene-treated rings and 77 +/- 5.1% in 17beta-estrogen-treated rings). In vivo ischemia and reperfusion resulted in significant endothelial dysfunction as evidenced by decreased vasorelaxation to acetylcholine (maximal relaxation: 48 +/- 5.5 versus 92 +/- 3.9% in normal SMA rings), but a normal relaxation response to an endothelium-independent vasodilator, acidified NaNO(2) (95 +/- 3.2%). Treatment with idoxifene at either 1 or 2 mg/kg/day, or 17beta-estrogen at 1 mg/kg/day for 4 days significantly preserved endothelial function (P <.01 versus vehicle). Taken together, these results demonstrate that idoxifene is an endothelium-dependent vasodilator and exerts significant endothelial protective effects against TNF alpha- and ischemia-reperfusion-induced endothelial injury. These results suggest that selective estrogen receptor modulators have therapeutic potential in diseases where endothelial dysfunction plays an important role.

Animals↗

PubMed1999

Human urotensin-II is a potent vasoconstrictor and agonist for the orphan receptor GPR14.

Urotensin-II (U-II) is a vasoactive 'somatostatin-like' cyclic peptide which was originally isolated from fish spinal cords, and which has recently been cloned from man. Here we describe the identification of an orphan human G-protein-coupled receptor homologous to rat GPR14 and expressed predominantly in cardiovascular tissue, which functions as a U-II receptor. Goby and human U-II bind to recombinant human GPR14 with high affinity, and the binding is functionally coupled to calcium mobilization. Human U-II is found within both vascular and cardiac tissue (including coronary atheroma) and effectively constricts isolated arteries from non-human primates. The potency of vasoconstriction of U-II is an order of magnitude greater than that of endothelin-1, making human U-II the most potent mammalian vasoconstrictor identified so far. In vivo, human U-II markedly increases total peripheral resistance in anaesthetized non-human primates, a response associated with profound cardiac contractile dysfunction. Furthermore, as U-II immunoreactivity is also found within central nervous system and endocrine tissues, it may have additional activities.

Amino Acid Sequence↗

PubMed1999

Pharmacology of eprosartan, an angiotensin II receptor antagonist: exploring hypotheses from clinical data.

Selective blockade of the angiotensin II AT1 receptor represents a novel mechanism for interrupting the renin-angiotensin system without altering the potential benefits of AT2 receptor stimulation. This selective inhibition produces none of the disadvantages associated with reduced bradykinin metabolism and angiotensin II generated by non-angiotensin-converting enzyme pathways. Eprosartan is a potent (1.4 nmol/L) AT1 receptor antagonist that competitively blocks angiotensin II-induced vascular contraction. In various animal models of disease, including hypertension and stroke, eprosartan is effective in reducing disease progression. Eprosartan also has sympathoinhibitory activity, as demonstrated by an inhibition of the pressor responses induced by activation of sympathetic outflow through spinal cord stimulation in pithed rats. In contrast, some of the other angiotensin II receptor antagonists, such as losartan, at equivalent angiotensin II blocking doses, have no effect on sympathetic nervous system activity. Because eprosartan can inhibit both the direct effects of angiotensin II as well as the indirect effects that are mediated by enhanced sympathetic neurotransmission, this may represent an important advance in the treatment of elevated systolic blood pressure.

Acrylates↗

PubMed1999

Apoptosis: a potential target for discovering novel therapies for cardiovascular diseases.

The realization that apoptosis is genetically programmed raises the exciting prospect that modulating apoptosis may provide novel approaches for treatment of cardiovascular diseases in which apoptosis has been demonstrated. Low molecular weight inhibitors of caspases and mitogen-activated protein kinases have been evaluated, with promising results in a variety of cardiovascular apoptotic models.

Animals↗

PubMed1999

Trigeminal nerve ganglion stimulation-induced neurovascular reflexes in the anaesthetized cat: role of endothelin(B) receptors in carotid vasodilatation.

1. The effects of intravenous administration of endothelin (ET) receptor antagonists SB-209670 (0.001-10.0 mg kg(-1)), SB-217242, SB-234551 (0.01-10.0 mg kg(-1)) and BQ-788 (0.001-1.0 mg kg(-1)) were investigated on trigeminal nerve ganglion stimulation-induced neurovascular reflexes in the carotid vasculature of the anaesthetized cat. Comparisons were made with sumatriptan (0.003-3.0 mg kg(-1)) and alpha-CGRP8-37 (0.001-0.1 mg kg(-1)). 2. Trigeminal nerve ganglion stimulation produced frequency related increases in carotid blood flow, reductions in carotid vascular resistance and non-frequency related increases in blood pressure. Guanethidine (3 mg kg(-1), i.v.) blocked trigeminal nerve ganglion-induced increases in blood pressure but had no effect on changes in carotid flow or resistance. Maximal reductions in carotid vascular resistance was observed at 10 Hz, and this frequency was selected to investigate the effects of drugs on trigeminal nerve ganglion stimulation-induced responses in guanethidine treated cats. 3. Saline, alpha-CGRP8-37 SB-209670 and BQ-788 had little or no effect on resting haemodynamic parameters. SB-217242 (10 mg kg(-1), n=3) produced a 56% reduction in arterial blood pressure whereas SB-233451 (10 mg kg(-1), n=3) produced a 30% reduction in carotid vascular resistance. Sumatriptan produced dose-related reductions in resting carotid flow and increases (max. 104% at 0.3 mg kg(-1), n = 5) in vascular resistance. 4. SB-209670 (n=6-7), SB-217242 (n=3) and BQ-788 (n=3) produced inhibition of trigeminal nerve ganglion stimulation-induced reductions in carotid vascular resistance. Saline, SB-234551, alpha-CGRP8-37 and sumatriptan had no effect. 5. These data demonstrate ET(B) receptor blockade attenuates the vasodilator effects of trigeminal nerve ganglion stimulation in the carotid vascular bed of guanethidine pretreated anaesthetized cats.

Anesthesia↗

PubMed1999

In vitro and in vivo characterization of intrinsic sympathomimetic activity in normal and heart failure rats.

Clinical studies conducted with carvedilol suggest that beta-adrenoceptor antagonism is an effective therapeutic approach to the treatment of heart failure. However, many beta-adrenoceptor antagonists are weak partial agonists and possess significant intrinsic sympathomimetic activity (ISA), which may be problematic in the treatment of heart failure. In the present study, the ISAs of bucindolol, xamoterol, bisoprolol, and carvedilol were evaluated and compared in normal rats [Sprague-Dawley (SD)], in rats with confirmed heart failure [spontaneously hypertensive heart failure (SHHF)], and in isolated neonatal rat cardiomyocytes. At equieffective beta1-adrenolytic doses, the administration of xamoterol and bucindolol produced a prolonged, equieffective, and dose-related increase in heart rate in both pithed SD rats (ED50 = 5 and 40 microgram/kg, respectively) and SHHF rats (ED50 = 6 and 30 microgram/kg, respectively). The maximum effect of both compounds in SHHF rats was approximately 50% of that observed in SD rats. In contrast, carvedilol and bisoprolol had no significant effect on resting heart rate in the pithed SD or SHHF rat. The maximum increase in heart rate elicited by xamoterol and bucindolol was inhibited by treatment with propranolol, carvedilol, and betaxolol (beta1-adrenoceptor antagonist) but not by ICI 118551 (beta2-adrenoceptor antagonist) in neonatal rat. When the beta-adrenoceptor-mediated cAMP response was examined in cardiomyocytes, an identical partial agonist/antagonist response profile was observed for all compounds, demonstrating a strong correlation with the in vivo results. In contrast, GTP-sensitive ligand binding and tissue adenylate cyclase activity were not sensitive methods for detecting beta-adrenoceptor partial agonist activity in the heart. In summary, xamoterol and bucindolol, but not carvedilol and bisoprolol, exhibited direct beta1-adrenoceptor-mediated ISA in normal and heart failure rats.

Adrenergic beta-Agonists↗

PubMed1999

Endothelin B receptor modulates inflammatory pain and cutaneous inflammation.

The role of endothelin B (ET(B)) receptors in inflammation and nociception was examined using ET(B) receptor knockout mice. Genotyping studies were used with tissues from ET(B)((+/+)), ET(B)((+/-)), and ET(B)((-/-)) mice to confirm the loss of ET(B) receptors. Algesia induced by phenylbenzoquinone was evident in the (+/+) mice, reduced by approximately 80% in the (+/-) mice, and absent in the (-/-) mice. Phenylbenzoquinone-induced algesia in (+/+) mice was inhibited 74% by the ET(B) receptor-selective antagonist A192621 (25 mg/kg p.o.), but unaffected by the ET(A) receptor-selective antagonist SB 234551 (25 mg/kg p.o.). Noninflammatory pain, induced by hotplate, was equivalent between (+/+) and (-/-) mice. The cutaneous inflammatory response to topical arachidonic acid (AA) also was evaluated. Whereas (+/+) mice had a marked inflammatory response to AA, the (+/-), and (-/-) mice had significantly reduced fluid phase responses (37 and 65% inhibition, respectively). Neutrophil infiltration also was reduced in the (+/-) and (-/-) mice (51 and 65% reduction, respectively). Topical administration of A192621 (500 microg/ear) in (+/+) mice inhibited AA-induced swelling (39%), whereas SB 234551 (500 microg/ear) was without effect. Collectively, these results implicate the ET(B) receptor in mediation of inflammatory pain and cutaneous inflammatory responses in mice.

Animals↗