Biomedical subjects

E H Ohlstein

Publications and source records attributed to E H Ohlstein.

At least 73 records · Page 4Linked to original sources

PubMed1998

Nonpeptide endothelin receptor antagonists. XI. Pharmacological characterization of SB 234551, a high-affinity and selective nonpeptide ETA receptor antagonist.

The present study describes the pharmacological profile of ((E)-alpha-[[1-butyl-5-[2-[(2-carboxyphenyl)methoxy]-4-methoxy-phenyl ]-1H-pyrazol-4-yl]methlene]-6-methoxy-1,3-benzodioxole-5-propanoic acid) (SB 234551), a high-affinity, nonpeptide endothelin type A (ETA)-selective receptor antagonist. In human cloned ETA and endothelin type B (ETB) receptors, SB 234551 produced a concentration-dependent displacement of [125I]-endothelin-1 with Ki values of 0.13 and 500 nM, respectively. SB 234551 elicited concentration-dependent, rightward competitive shifts in the endothelin-1 concentration-response curves in isolated rat aorta and isolated human pulmonary artery (ETA receptor-mediated vascular contraction) with Kb values of 1.9 and 1.0 nM, respectively. SB 234551 antagonized ETB receptor-mediated vasoconstriction in the isolated rabbit pulmonary artery, as demonstrated by concentration-dependent, rightward shifts in the sarafotoxin S6c concentration-response curves (Kb = 555 nM). SB 234551 produced weak functional inhibition of sarafotoxin S6c-mediated endothelium-dependent relaxation (IC50 = 7 microM). SB 234551 (10 microM) had no significant effect against contraction produced by several other vasoactive agents and did not significantly influence radioligand binding to a number of diverse receptors. SB 234551 (0. 1-1.0 mg/kg i.v.) dose-dependently inhibited the pressor response to exogenous endothelin-1 in conscious rats. In vivo pharmacokinetic analysis in the rat demonstrated that SB 234551 was rapidly absorbed from the GI tract with a bioavailability of 30%. SB 234551 had a plasma half-life of 125 min and a systemic clearance of 25.0 ml/min/kg. The present study demonstrates that SB 234551 is an antagonist with high affinity for the ETA receptor, while sparing the ETB receptor. SB 234551 is a new pharmacological tool that should assist in the elucidation of the role of endothelin in pathophysiology.

Animals↗

PubMed1997

Identification, characterization, and functional role of phosphodiesterase type IV in cerebral vessels: effects of selective phosphodiesterase inhibitors.

The role of the phosphodiesterase type IV isozyme (PDE IV) in the regulation of cerebrovascular tone was investigated in the canine basilar artery in vitro and in vivo. The PDE isozymes extracted from the canine basilar artery were isolated by diethylaminoethanol (DEAE)-Sepharose affinity chromatography and identified based on sensitivity to isozyme-selective PDE inhibitors. [3H]cAMP hydrolysis was observed in one major and one minor peak of activity. The predominant peak was inhibited by the addition of cGMP (25%), siguazodan (26%), rolipram (39%), and the combination of siguazodan and rolipram (95%). Selective PDE IV inhibitors BRL 61063, rolipram, and denbufylline were equieffective inhibitors of [3H]-ccAMP hydrolysis mediated by PDE IV isolated from the canine basilar artery [concentrations producing 50% inhibition (IC50S) = 0.21 +/- 0.05 microM, 0.67 +/- 0.23 microM, and 0.73 +/- 0.16 microM, respectively]. In precontracted isolated ring segments of the canine basilar artery, selective PDE IV inhibitors produced potent and complete relaxation (IC50S < 150 nM). In contrast, zaprinast (a selective PDE V inhibitor) and siguazodan (a selective PDE III inhibitor) produced only weak relaxation of the basilar artery (IC50S = 4.5 microM and > 10 microM, respectively). Vasorelaxation produced by PDE IV inhibitors was not altered by removing the endothelium, 1-NAME, or adenosine receptor antagonism. In a canine model of acute cerebral vasospasm, all three selective PDE IV inhibitors reversed basilar artery spasm produced by autologous blood without altering mean arterial blood pressure. In contrast, prolonged treatment with BRL 61063 failed to alter the development of basilar spasm in the two hemorrhage canine models of chronic cerebral vasospasm. Denbufylline-induced relaxation in vitro was also significantly impaired in basilar arteries obtained from the model of chronic vasospasm. In conclusion, PDE IV appears to be the predominant isozyme regulating vascular tone mediated by cAMP hydrolysis in cerebral vessels. In addition, vasorelaxation modulated by PDE IV is compromised in chronic cerebral vasospasm associated with subarachnoid hemorrhage.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1997

Inhibition of sympathetic outflow by the angiotensin II receptor antagonist, eprosartan, but not by losartan, valsartan or irbesartan: relationship to differences in prejunctional angiotensin II receptor blockade.

It is well established that angiotensin II can enhance sympathetic nervous system function by activating prejunctional angiotensin II type I (AT1) receptors located on sympathetic nerve terminals. Stimulation of these receptors enhances stimulus-evoked norepinephrine release, leading to increased activation of vascular alpha 1-adrenoceptors and consequently to enhanced vasoconstriction. In the present study, the effects of several chemically distinct nonpeptide angiotensin II receptor antagonists were evaluated on pressor responses evoked by activation of sympathetic outflow through spinal cord stimulation in the pithed rat. Stimulation of thoracolumbar sympathetic outflow in pithed rats produced frequency-dependent pressor responses. Infusion of sub-pressor doses of angiotensin II (40 ng/kg/min) shifted leftward the frequency-response curves for increases in blood pressure, indicating augmented sympathetic outflow. Furthermore, pressor responses resulting in spinal cord stimulation were inhibited by the peptide angiotensin II receptor antagonist, Sar1, Ile8 [angiotensin II] (10 micrograms/kg/min). These results confirm the existence of prejunctional angiotensin II receptors at the vascular neuroeffector junction that facilitate release of norepinephrine. The nonpeptide angiotensin II receptor antagonist, eprosartan (0.3 mg/kg i.v.), inhibited the pressor response induced by spinal cord stimulation in a manner similar to that observed with the peptide antagonist, Sar1, Ile8[angiotensin II]. In contrast, equivalent doses (0.3 mg/kg i.v.) of other nonpeptide angiotensin II receptor antagonists, such as losartan, valsartan, and irbesartan, had no effect on spinal cord stimulation of sympathetic outflow in the pithed rat. Although the mechanism by which eprosartan, but not the other nonpeptide angiotensin II receptor antagonists, inhibits sympathetic outflow in the pithed rat is unknown, one possibility is that eprosartan is a more effective antagonist of prejunctional angiotensin II receptors that augment neurotransmitter release. Because eprosartan is more effective in inhibiting sympathetic nervous system activity compared to other chemically distinct nonpeptide angiotensin II receptor antagonists, eprosartan may be more effective in lowering systolic blood pressure and in treating isolated systolic hypertension.

Acrylates↗

PubMed1997

Nonpeptide endothelin receptor antagonists. VIII: attentuation of acute hypoxia-induced pulmonary hypertension in the dog.

It has been proposed that endothelin-1 (ET-1), a potent endogenous vasoactive peptide, may play an important role in the regulation of pulmonary blood flow. The purpose of the present study was to characterize the effects of ET-1 and a nonpeptide mixed ET(A) and ET(B) receptor antagonist, SB 209670, in isolated segments of the canine pulmonary artery and to examine the effects of SB 209670 in a canine model of acute hypoxia-induced pulmonary hypertension. In isolated segments of the pulmonary artery, SB 209670 (3-300 nM) produced a concentration-dependent antagonism of contraction elicited by ET-1 (pA2 = 8.9; slope = 0.9) and had no effect on phenylephrine responses. In addition, SB 209670 antagonized the small, endothelium-dependent relaxation induced by sarafotoxin 6c in phenylephrine (10 microM)-precontracted vessels (pKB = 8.6). In anesthetized dogs, the driving pressure across the pulmonary circulation increased approximately 100% during the hypoxic period (area under the curve [AUC] = 267.1 +/- 25.3 mm Hg x min). SB 209670 treatment (3 and 30 microg/kg/min i.v.) reduced pulmonary vascular resistance and produced a profound dose-related inhibition of hypoxia-induced pulmonary hypertension (AUC = 158.3 +/- 22.7 mm Hg x min and 50.1 +/- 4.9 mm Hg x min, respectively). None of the other hemodynamic or arterial blood gas parameters differed significantly in the vehicle and treatment groups. In addition, SB 209670 produced a significant reversal of hypoxia-induced pulmonary hypertension (AUC = 267.1 +/- 25.3 mm Hg x min vs. 167.8 +/- 23.4 mm Hg x min) when administered at the plateau of the hypoxic response. It was found that SB 209670 administration significantly elevated plasma levels of ET-1-LI (> or = 25-fold). These results suggest that ET-1 is an important mediator of hypoxia-induced pulmonary hypertension in the dog and that SB 209670, a potent and selective mixed ET(A) and ET(B)receptor antagonist in the pulmonary circulation, may represent an important therapeutic approach to the treatment of pulmonary hypertension.

Animals↗

PubMed1997

Carvedilol, a multiple-action neurohumoral antagonist, inhibits mitogen-activated protein kinase and cell cycle progression in vascular smooth muscle cells.

Recent findings that the multiple-action neurohumoral antagonist carvedilol inhibits the mitogenic effects of a broad variety of mitogens and produces marked protection against neointima formation after balloon angioplasty injury prompted further study into the molecular and biochemical mechanism of action. In the present study, the effects of carvedilol on mitogen-activated protein (MAP) kinase activity and cell cycle progression were evaluated. Carvedilol produced significant concentration-dependent inhibition of mitogen-induced MAP kinase activity in rat smooth muscle cells. Furthermore, when MAP kinase was purified from mitogen-stimulated cells by FPLC Mono Q chromatography, carvedilol produced direct enzyme inhibition. In the cell-free assay, carvedilol (10 microM) produced 50% inhibition of MAP kinase activity. Cell flow cytometry studies revealed that quiescent rat aortic smooth muscle cells showed 96% of the cell population in the G0/G1 phase of the cell cycle. The addition of serum (10%) increased the number of cells in S and G2/M phases 20% to 40%, respectively. Carvedilol (10 microM) significantly decreased (30-50%) the number of cells in S and G2/M phase. In addition, carvedilol significantly inhibited (>70%) serum-induced stimulation of the S phase-specific marker thymidine kinase. These data suggest that the antimitogenic actions of carvedilol on vascular smooth muscle may be in part due to the inhibition of MAP kinase activity and regulation of cell cycle progression.

Animals↗

PubMed1996

Interferon-inducible protein-10 involves vascular smooth muscle cell migration, proliferation, and inflammatory response.

Interferon-inducible protein-10 (IP-10) is a member of the C-X-C chemokine family. Using mRNA differential display, we isolated a rat homologue to murine and human IP-10 from lipopolysaccharide-stimulated carotid arteries. Our studies demonstrated that IP-10 is a potent mitogenic and chemotactic factor for vascular smooth muscle cells, the critical features of smooth muscle cells for their contribution to the pathogenesis of atherosclerosis and restenosis. IP-10 induced a concentration-dependent stimulation of DNA synthesis, cell proliferation, and cell migration of rat aortic smooth muscle cells. A concentration- and time-dependent IP-10 mRNA induction was observed in lipopolysaccharide- or interferon-gamma-stimulated, but not interleukin-1beta- or tumor necrosis factor-alpha-stimulated smooth muscle cells. A marked synergistic effect on IP-10 mRNA expression was observed when smooth muscle cells were challenged with interferon-gamma together with interleukin-1beta or tumor necrosis factor-alpha. Furthermore, IP-10 mRNA expression was induced in the rat carotid artery after balloon angioplasty. The mitogenic and chemotactic features of IP-10 for smooth muscle cells, along with its discrete induction in cultured vascular smooth muscle cells and in carotid arteries after balloon angioplasty (neointima formation) suggest that IP-10 may play an active and distinct role in vascular remodeling processes.

Angioplasty, Balloon↗

PubMed1996

Endothelin receptors: receptor classification, novel receptor antagonists, and potential therapeutic targets.

The development of endothelin receptor antagonists has progressed rapidly since the initial discovery of endothelin. Highly potent, orally active nonpeptide endothelin receptor antagonists have been identified, and are being used as pharmacological tools to elucidate the role of endothelin in pathological disorders. Subtype selective endothelin receptor antagonists will also be useful in understanding the physiological and pathological roles of the different subtypes of the endothelin receptors. The selectivity profile for the ideal endothelin receptor antagonist is presently unknown, and it may actually be that the optimal profile for a compound may depend on the clinical indication. In the near future, data from clinical trials with endothelin receptor antagonists will become available and will help to establish the role of endothelin in the etiology of human disease, as well as to provide valuable information concerning the optimum endothelin receptor subtype selectivity for antagonists needed for therapeutic agents.

Amino Acid Sequence↗

PubMed1996

California dreamin' 'bout endothelin: emerging new therapeutics.

Progress in our understanding of endothelins has been extremely rapid since their discovery in 1988. A number of pharmaceutical companies have developed potent, orally active, nonpeptide endothelin receptor antagonists with efficacies in a wide variety of animal disease models and potential for treating human disease. However, only time will tell whether or not these compounds are developed into drugs that are perceived as worthy of a place in the therapeutic marketplace. If this is the case, endothelin will have been promoted from the status of striking scientific discovery to therapeutic target in a remarkably short period.

Animals↗

PubMed1996

Isolation and characterization of BART-1: A novel balloon angioplasty responsive transcript in rat carotid arteries.

In previous studies, differential display analysis of balloon angioplasty-damaged rat carotid arteries identified a temporally expressed partial cDNA termed RC9. This message is undetectable in undamaged vessels, reaches maximal levels 3 days post-procedure, and reduces to half-maximal expression by 14 days post angioplasty. Using RC9 to screen a cDNA library, we now report the isolation and characterization of a full-length clone, termed BART-1. BART-1 is 98% homologous to RC9 and shows the same mRNA expression pattern as RC9 in rat carotid arteries subject to balloon angioplasty. Northern analysis of various rat tissues reveals tissue specificity and possible differential processing. Neither the nucleic acid nor amino acid sequences demonstrate similarity to previously reported expressed sequences. Predicted amino acid analysis reveals two strongly hydrophilic and one hydrophobic region, suggesting a type II integral membrane protein. The cDNA sequence hybridized to genomic DNA from a variety of species, suggesting evolutionary conservation. Thus, BART-1 mRNA appears to represent an inducible, tissue-specific transcript encoding a putative integral membrane protein transiently expressed in response to vascular trauma.

Amino Acid Sequence↗

PubMed1996

Spinal endothelin content is elevated after moderate local trauma in the rat to levels associated with locomotor dysfunction after intrathecal injection.

The role of endothelin (ET) in the pathophysiology of secondary neural damage after experimental spinal cord injury (SCI) was examined in a rat model of weight-drop contusion injury. Initial studies demonstrated a significant increase in spinal ET concentrations in a 7.5-mm segment of tissue (centered at the impact site) at 30 min, 4 h, and 24 h after a moderate (50 g-cm) contusion injury. Subsequent experiments were aimed at reproducing these elevations by the intrathecal (i.t.) administration of ET and observing the effect on locomotor function. These studies showed that i.t. dosage of 9.6 ng produced spinal cord elevations of ET similar to those seen 30 min after moderate SCI as well as mild locomotor deficits. A 48 ng dose of ET resulted in moderate to severe locomotor deficits that were associated with spinal ET elevations much greater than those seen after injury. The mild deficits attributable to the lower dose of ET could contribute to the pathophysiological actions of other purported secondary injury mediators. The more pronounced locomotor deficits associated with the higher dose could be of relevance for severe SCI.

Animals↗

PubMed1996

Comparison of endothelin B (ETB) receptors in rabbit isolated pulmonary artery and bronchus.

1. To explore potential differences between endothelin (ET) receptors in airway versus vascular smooth muscle from the same species, the ETB receptors mediating contractions produced by ET-1, ET-3 and the selective ETB ligands, sarafotoxin S6c (S6c) and BQ-3020, in rabbit bronchus and pulmonary artery were investigated by use of peptide and non-peptide ET receptor antagonists. 2. In rabbit pulmonary artery SB 209670 (10 microM), a mixed ETA/ETB receptor antagonist, was a more potent antagonist of contractions produced by S6c (pKB = 7.7; n = 9; P < 0.05), than those elicited by ET-1 (pKB = 6.7; n = 6) or ET-3 (pKB = 6.7; n = 5). BQ-788 (10 microM), an ETB receptor antagonist, inhibited responses produced by ET-3 (pKB = 5.1; n = 8), BQ-3020 (pKB = 5.2; n = 4) or S6c (pKB = 6.2; n = 9; P < 0.05 compared to potency versus ET-3- or BQ-3020-induced contractions), but was without inhibitory effect on ET-1-induced contractions (n = 5). RES-701 (10 microM), another selective ETB receptor antagonist, was without effect on contractions produced by S6c (n = 4) or ET-1 (n = 4), and potentiated ET-3- (n = 5) or BQ-3020-induced responses (n = 4). 3. The combination of BQ-788 (10 microM) and BQ-123 (10 microM), an ETA-selective receptor antagonist, antagonized contractions produced by lower concentrations of ET-1 (1 and 3 nM) in rabbit pulmonary artery, but was without effect on responses elicited by higher concentrations of ET-1 (n = 5). The combination of RES-701 (10 microM) and BQ-123 (10 microM) potentiated responses elicited by ET-1, producing a 3.7 fold shift to the left in the agonist concentration-response curve (n = 5). 4. In rabbit bronchus SB 209670 (3 microM) had similar potency for antagonism of contractions produced by ET-1 (pKB = 6.3; n = 6), ET-3 (pKB = 6.5; n = 6) or S6c (pKB = 6.1; n = 8). BQ-788 (3 microM) was without effect on responses elicited by ET-1, ET-3 or S6c (n = 6) but antagonized BQ-3020-induced contractions (pKB = 6.4; n = 4). RES-701 (3 microM) was without effect on contractions produced by S6c (n = 6) or BQ-3020 (n = 4), and potentiated rather than antagonized ET-1- or ET-3-induced responses (n = 6), reflected by a significant (about 6 fold) shift to the left in ET-1 or ET-3 concentration-response curves. The combination of BQ-788 (3 microM) and BQ-123 (3 microM) was without effect on contractions produced by ET-1 in rabbit bronchus (n = 6). The combination of RES-701 (3 microM) and BQ-123 (3 microM) potentiated responses elicited by ET-1, producing a 5.2 fold shift to the left in the agonist concentration-response curve (n = 5). 5. BQ-123 (3 or 10 microM), an ETA-selective receptor antagonist, was without effect on ET-1, ET-3 or S6c concentration-response curves (n = 3-6) in rabbit pulmonary artery or rabbit bronchus. 6. These data indicate that contractions induced by ET-1, ET-3, S6c and BQ-3020 in rabbit pulmonary artery or rabbit bronchus appear to be mediated predominantly via stimulation of ETB receptors. However, the qualitative and quantitative differences in the relative profiles of the various structurally diverse peptide and non-peptide antagonists examined suggests that responses produced by the ET ligands may not be mediated by a homogeneous ETB receptor population. In addition, the results suggest that differences exist in the ETB receptors mediating contraction in pulmonary vascular versus airway tissues in the same species. These receptors are not very sensitive to the standard ETB receptor antagonists, BQ-788 and RES-701. Furthermore, the results also provide further evidence that the potencies of ET receptor antagonists depend upon the ET agonist.

Animals↗

PubMed1996

Osteopontin expression in platelet-derived growth factor-stimulated vascular smooth muscle cells and carotid artery after balloon angioplasty.

Osteopontin (OPN), an arginine-glycine-aspartate (RGD)-containing adhesive glycoprotein, is constitutively expressed in rat aorta and carotid arteries and is markedly elevated in response to vascular injury. OPN is chemotactic for vascular smooth muscle cells (SMCs), suggesting a role in vascular remodeling. However, the mechanism for the regulation of OPN expression is poorly understood. In the present study, the effect of platelet-derived growth factor (PDGF) on OPN mRNA expression was investigated in cultured rat aortic SMCs (RASMCs). When RASMCs were stimulated with 1 nmol/L PDGF, a 2.4-fold increase in OPN mRNA expression was observed at 3 hours (P < .05) that peaked at 14 hours with a 6.7-fold increase (P < .001). This induction was blocked by a monoclonal anti PDGF antibody. Further studies revealed that OPN mRNA expression was induced by PDGF-AB or PDGF-BB but not by PDGF-AA, indicating that only the beta-type PDGF receptor mediates this response. Compared with basic fibroblast growth factor, epidermal growth factor, transforming growth factor-beta, and interleukin-1 beta, PDGF was the most potent factor studied to induce OPN mRNA expression in RASMCs. Immunohistochemical studies demonstrated the elevation of OPN protein in PDGF-stimulated RASMCs. The temporal expression of OPN mRNA after rat carotid artery balloon angioplasty as assessed by both reverse transcription-polymerase chain reaction and Northern blot analysis revealed a 1.5-fold increase at 6 hours (P < .01) that peaked at 1 and 3 days with a 3.1-fold increase (P < .001). Immunohistochemical studies of carotid artery after angioplasty localized OPN expression in the medical SMCs at 1 day, ie. at a time of significant platelet adherence to the injured vessel, and thereafter to the intimal lesion during neointimal formation. These data suggest that OPN expression in vascular SMCs is regulated by PDGF through the beta-type PDGF receptor in vitro, and possibly in vivo in situations that involve PDGF released from platelets or other cellular sources, such as blood vessels after angioplasty injury.

Angioplasty, Balloon↗

PubMed1996

Expression of endothelin-1, endothelin-3, endothelin-converting enzyme-1, and endothelin-A and endothelin-B receptor mRNA after angioplasty-induced neointimal formation in the rat.

Endothelins (ETs) are potent vasoconstrictors known to play a role in tissue remodeling after vascular wall injury. The molecular mechanisms for the expression and functions of ETs and their receptors after carotid artery angioplasty are not fully understood. Using quantitative reverse transcription and polymerase chain reaction, the present study demonstrates the temporal mRNA expression of ET-converting enzyme-1 (ECE-1), preproET-1, preproET-3, and both ETA and ETB receptors after rat carotid artery balloon angioplasty. A significant increase in ECE-1 mRNA was observed at 6 hours (1.8-fold increase over control, P < .01) and 24 hours (1.7-fold increase, P < .01) in carotid arteries after angioplasty. In contrast, a significant increase in preproET-1 mRNA levels was not observed until 3 days (1.9-fold increase, P < .05) and 7 days (2.1-fold increase, P < .05). A similarly delayed increase in preproET-3 mRNA was observed at 7 days (2.8-fold increase, P < .05) and 14 days (2.6-fold increase, P < .05) after angioplasty. A parallel but marked increase in ETA and ETB receptor mRNAs compared with preproET-1 and -3 messages was observed after angioplasty. The levels of ETA receptor mRNA were elevated 29.3-fold (P < .001) and 24.3-fold (P < .01) at 3 and 7 days, respectively, after angioplasty. The increase in ETB receptor mRNA occurred slightly earlier than the increase in ETA receptor mRNA, showing 15.1-fold increase at 1 day (P < .001) and 11.3-fold increase at 3 days (P < .01) after angioplasty. Immunohistochemical studies using anti-ET antibodies demonstrated a corresponding increase in ET immunoactivity, which was distributed mainly in the neointimal cells 14 days after angioplasty. The increases in ECE-1, ET-1, and ET-3 and their receptor expression after balloon angioplasty suggest that these proteins play an active role in the pathogenesis of neointimal formation.

Animals↗

PubMed1996

Nonpeptide endothelin receptor antagonists. VI: Pharmacological characterization of SB 217242, a potent and highly bioavailable endothelin receptor antagonist.

This study describes the pharmacological characterization of SB 217242, a highly potent orally bioavailable nonpeptide antagonist of both endothelin type A (ETA) and endothelin type B (ETB) receptors. In human cloned ETA and ETB receptors, SB 217242 produced concentration-dependent displacement of [125]I-endothelin-1 (ET-1) in both receptor subtypes with Ki values of 1.1 and 111 nM, respectively. SB 217242 produced concentration-dependent, parallel rightward shifts in the ET-1 concentration-response curves in rat isolated aorta and human isolated pulmonary artery (ETA receptor-mediated vascular contraction) with Kb values of 4.4 and 5.0 nM, respectively. SB 217242 was 4-, 62- and 125-fold more potent as an ETA receptor antagonist than the previously reported compounds BQ-123, PD 142893 and Ro 46-2005, respectively. SB 217242 (10 microM) did not produce significant effects against contraction produced by other vasoactive agents. SB 217242 produced concentration-dependent antagonism of responses produced by ETB receptor activation as demonstrated by antagonism of sarafotoxin S6c-mediated contraction in the rabbit isolated pulmonary artery with a Kb value of 352 nM. In vitro cell monolayers of Caco-2 cells had high permeability to SB 217242. In vivo pharmacokinetics in the rat confirmed that SB 217242 was rapidly absorbed from the gastrointestinal tract with a bioavailability of 66%. The SB 217242 plasma half-life in rats after intraduodenal administration was 3.3 hr, with a systemic clearance of 27.3 ml/min/kg. Orally administered SB 217242 (0.3-30 mg/kg) produced dose-dependent inhibition of the pressor response to exogenous ET-1 in conscious rats; with a dose of 30 mg/kg p.o., inhibition was observed for at least 5.5 hr. The present study demonstrates that SB 217242 is a highly potent antagonist of both ETA and ETB receptors. In addition, SB 217242 has high in vitro permeability and high oral bioavailability. SB 217242 represents a new orally active pharmacological tool that should assist in the elucidation of the chronic role of endothelin in pathophysiology.

Animals↗

PubMed1996

Chronic carvedilol reduces mortality and renal damage in hypertensive stroke-prone rats.

The effects of carvedilol, a novel vasodilating beta-blocker and antioxidant, and propranolol on survival, neurobehavioral deficits, cardiovascular parameters, plasma renin, plasma aldosterone levels and renal pathology were determined in stroke-prone spontaneously hypertensive rats. Stroke-prone spontaneously hypertensive rats were allowed access to 1% NaCl as the drinking solution and a high fat diet supplemented with carvedilol (1200 or 2400 ppm) or propranolol (2400 ppm). The control group consisted of stroke-prone spontaneously hypertensive rats placed on the same diet with no drug supplement. Animals fed propranolol had a blood level of 864 +/- 68 ng/ml, whereas carvedilol-fed animals had blood levels of 24 +/- 4 ng/ml at 1200 ppm and 471 +/- 145 ng/ml at 2400 ppm. Carvedilol and propranolol treatment resulted in significant beta adrenoceptor blockade. Both compounds reduced heart rate, but had no significant effects on systolic arterial blood pressure. Carvedilol- and propranolol-treated animals also exhibited significant, prolonged protection from neurobehavioral deficits and mortality (P < .01). Elevated plasma renin activity and aldosterone levels seen in untreated controls were significantly decreased by propranolol (P < .05), and to a considerably greater extent by the same dose of carvedilol (P < .01). Carvedilol decreased renal histopathological damage and cardiac hypertrophy to a greater extent (P < .01) than propranolol (at equal doses). Both carvedilol (P < .01)- and propranolol (P < .01)-treated animals had considerably reduced renal damage at 18 weeks of treatment. Carvedilol reduced renal damage more than propranolol (P < .05). In addition, the lower (1200 ppm) dose of carvedilol, which decreased neurobehavioral deficits and mortality, had no significant effects on organ mass or renal function, but significantly (P < .01) reduced renal damage. These data indicate that both beta adrenoceptor blockers, especially carvedilol to a considerably greater degree, convey significant protection in a genetic model of severe hypertension that results in renal and cardiovascular organ pathology, neurobehavioral deficits and premature death.

Adrenergic beta-Antagonists↗

PubMed1996

Expression of 14-3-3 gamma in injured arteries and growth factor- and cytokine-stimulated human vascular smooth muscle cells.

One of the most critical cellular events in disease states such as vascular restenosis is the cytokine-induced activation of vascular smooth muscle cells (VSMCs) resulting in intimal thickening. Identification of the molecular mechanisms of VSMC activation is crucial in understanding the initiation of vascular restenosis. In this report, we show that one 14-3-3 protein family isoform, gamma, is transcriptionally up-regulated in rat carotid arteries after balloon angioplasty. 14-3-3 gamma protein induction localizes to both the media and neointima in such injured vessels. Because it has been shown that some members of the 14-3-3 family may play an important role in cellular proliferation by binding to and activating the protein kinase Raf-1 and VSMCs constitute the major cellular component of the restenotic lesion, we investigated the expression of this message in serum- and cytokine-stimulated human VSMCs. Both serum and selected cytokines induce 14-3-3 gamma mRNA and protein, the magnitude of which correlates with the degree of cellular stimulation. 14-3-3 gamma mRNA, however, does not increase when other cell types are stimulated with specific growth factors. Human tissue distribution of 14-3-3 gamma mRNA indicates that in contrast to other 14-3-3 proteins, the gamma isoform is highly expressed in VSMCs and skeletal and heart muscle, suggesting an important role for the gamma isoform in muscle tissue as well. These results indicate that 14-3-3 gamma expression increases in response to vessel damage and proliferative signals and may implicate a role for the gamma isoform of 14-3-3 in VSMC activation and metabolism.

14-3-3 Proteins↗

PubMed1995

Pharmacology of a potent long-acting imidazole-5-acrylic acid angiotensin AT1 receptor antagonist.

The angiotensin II antagonistic activity of SB 203220, [E-alpha-[[2-butyl-1-(4-carboxy-1-naphthalenyl)methyl]-1H- imidazol-5-yl]-methylene]-2-thiophene-propanic acid], was examined in several in vitro and in vivo assays. SB 203220 displaced [125I]angiotensin II binding from a variety of tissues including the cloned human AT1 receptor (IC(50)5-15 nM). SB 203220 (10 microM) did not interact with AT2, endothelin (ETA and ETB) or calcitonin gene-related peptide receptors. [3H]SB 203220 bound with high affinity to the AT1 receptor (Kd = 4.9 nM), but dissociated from the receptor at a much slower rate when compared to [3H]SK&F 108566. SB 203220 antagonized intracellular Ca2+ mobilization induced by angiotensin II in rat vascular smooth muscle cells and exhibited a selective and partially insurmountable antagonism of angiotensin II-induced contraction in isolated rabbit aorta. In the aorta, SB 203220 produced a concentration-dependent parallel shift in the concentration-response curve to angiotensin II [EC30 = 5.94 +/- 1.6 10(-11) M] and depressed the maximal contractile response to angiotensin II by approximately 35%. The antagonistic effect of SB 203220 in rabbit aorta was slowly reversible compared to SK&F 108566. SB 203220 displayed no agonist activity and had no effect on the contractile responses to KCl, endothelin-1 or norepinephrine. In rats, SB 203220 at 10 mg/kg i.v. inhibited angiotensin II-induced aldosterone release. Intraduodenal or oral administration of SB 203220 (1-10 mg/kg) to conscious rats and dogs inhibited the pressor responses to exogenous angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1995

In vivo pharmacological characterization of the non-peptide endothelin receptor antagonist SB 209670.

1. The aim of the present study was to assess the ability of SB 209670, a high affinity non-peptide endothelin receptor antagonist (0.4 and 18 nM Kis at human cloned ETA and ETB receptors, respectively), to inhibit the haemodynamic actions of endothelin-1 in vivo. 2. Systemic administration of (+/-)-SB 209670, given either as a bolus i.v. injection or as a continuous i.v. infusion, did not alter basal haemodynamic parameters in the anaesthetized rat. 3. Infusion of (+/-)-SB 209670 (10 micrograms kg-1 min-1) selectively inhibited the depressor and carotid vasodilator response to exogenous endothelin-1: 100 micrograms kg-1 min-1 was required to inhibit significantly the biphasic haemodynamic actions of endothelin-1. The haemodynamic actions of angiotensin II and calcitonin gene-related peptide were unaltered by 100 micrograms kg-1 min-1 (+/-)-SB 209670. 4. Bolus i.v. administration of (+/-)-SB 209670 (1 mg kg-1) selectively inhibited the depressor and carotid vasodilator actions of endothelin-1: 10 mg kg-1 (+/-)-SB 209670 was required to inhibit the secondary vasoconstrictor actions of endothelin-1. 5. (+/-)-SB 209670 (10 mg kg-1) was also effective at antagonizing the pressor actions of endothelin-1 in the conscious rat for up to 3 h after intraduodenal administration thereby demonstrating that the antagonist was bioavailable upon enteric administration. This dose of (+/-)-SB 209670 did not alter basal haemodynamic parameters in the conscious rat. 6. Thus, ( +/- )-SB 209670 is an effective endothelin receptor antagonist in vivo. Using the doses defined in this study, SB 209670 may, therefore, serve as a useful tool for understanding the role of endogenous endothelin-I in the control of cardiovascular function under both physiological and pathophysiological conditions.

Angiotensin II↗