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Biomedical subjects

W A Bax

Publications and source records attributed to W A Bax.

At least 19 recordsLinked to original sources
PubMed2000

Human isolated coronary artery contraction to sumatriptan characterised by the selective 5-HT1B/1D receptor antagonist GR55562.

The antimigraine drug, sumatriptan, contracts the human coronary artery both in vivo and in vitro. Because sumatriptan has been associated with cardiac side effects, it is important to characterise the receptor involved in sumatriptan-induced coronary artery contraction. Using the agonists sumatriptan and 5-carboxamidotryptamine and the selective 5-HT1B/1D receptor antagonist GR55562, we have investigated the involvement of 5-HT1B/1D receptors in the contraction of the human isolated coronary artery. Contractions to sumatriptan (pEC50: 6.1+/-0.2, maximal effect: 21+/-4% of 100 mM K+-induced contraction) were competitively antagonised by GR55562. The pA2 of GR55562 (7.40+/-0.16) was in accord with its reported affinity at the human 5-HT1B receptor. Since the contractions to 5-carboxamidotryptamine did not reach a maximum with the highest concentration used (10 microM), pEC50 values could not be calculated for Schild analysis. However, using the pEC10%/K+ values (negative logarithm of the concentration needed to induce 10% of the contraction to 100 mM K+), GR55562 proved a less potent antagonist against 5-carboxamidotryptamine than against sumatriptan. These results show that sumatriptan contracts the human isolated coronary artery via 5-HT1B/1D receptors, most probably the 5-HT1B subtype. 5-Carboxamidotryptamine may contract the human isolated coronary artery, at least partly, via a novel yet to be characterised, receptor.

Benzamides↗
PubMed1999

Human isolated coronary artery contraction to sumatriptan: a post hoc analysis.

A post hoc analysis was performed on concentration response curves to sumatriptan in 62 human isolated coronary arteries. We determined whether donor-related clinical characteristics (age, sex, cause of death) and properties of the coronary artery (functional endothelial integrity, muscle mass) were related to the potency and efficacy of sumatriptan in contracting the human isolated coronary artery. The efficacy of sumatriptan was inversely related to the functional integrity of the vessel endothelium. Thus, contrary to expectation, coronary artery constriction to sumatriptan seems to be more pronounced in patients with nondiseased coronary arteries where the endothelium is intact. Nevertheless, in view of the high coronary reserve in these patients, myocardial ischemia after the use of sumatriptan is unlikely to occur, whereas in patients with coronary artery disease even a small contraction may be deleterious.

Adult↗
PubMed1998

Coronary side-effect potential of current and prospective antimigraine drugs.

BACKGROUND: The antimigraine drugs ergotamine and sumatriptan may cause angina-like symptoms, possibly resulting from coronary artery constriction. We compared the coronary vasoconstrictor potential of a number of current and prospective antimigraine drugs (ergotamine, dihydroergotamine, methysergide and its metabolite methylergometrine, sumatriptan, naratriptan, zolmitriptan, rizatriptan, avitriptan). METHODS AND RESULTS: Concentration-response curves to the antimigraine drugs were constructed in human isolated coronary artery segments to obtain the maximum contractile response (Emax) and the concentration eliciting 50% of Emax (EC50). The EC50 values were related to maximum plasma concentrations (Cmax) reported in patients, obtaining Cmax/EC50 ratios as an index of coronary vasoconstriction occurring in the clinical setting. Furthermore, we studied the duration of contractile responses after washout of the acutely acting antimigraine drugs to assess their disappearance from the receptor biophase. Compared with sumatriptan, all drugs were more potent (lower EC50 values) in contracting the coronary artery but had similar efficacies (Emax <25% of K+-induced contraction). The Cmax of avitriptan was 7- to 11-fold higher than its EC50 value, whereas those of the other drugs were <40% of their respective EC50 values. The contractile responses to ergotamine and dihydroergotamine persisted even after repeated washings, but those to the other drugs declined rapidly after washing. CONCLUSIONS: All current and prospective antimigraine drugs contract the human coronary artery in vitro, but in view of low efficacy, these drugs are unlikely to cause myocardial ischemia at therapeutic plasma concentrations in healthy subjects. In patients with coronary artery disease, however, these drugs must remain contraindicated. The sustained contraction by ergotamine and dihydroergotamine seems to be an important disadvantage compared with sumatriptan-like drugs.

Adolescent↗
PubMed1998

BMS-181885, a 5-HT1B/1D receptor ligand, in experimental models predictive of antimigraine activity and coronary side-effect potential.

Many acutely acting antimigraine drugs have the ability to constrict porcine arteriovenous anastomoses as well as the human isolated coronary artery. These two experimental models seem to serve as indicators, respectively, for the therapeutic and coronary side-effect potential of the compounds. Using these two models, we have investigated the effects of BMS-181885 (3-[3-[4-(5-methoxy-4-pyrimidyl)-1-piperazinyl]propyl]-5-(1,2-dioxo-4-me thyl-3-cyclobuten-3-yl)amino-1H-indole), a 5-HT1B/1D receptor ligand. In anaesthetised pigs, BMS-181885 (10, 30, 100 and 300 microg kg(-1)) decreased the total carotid blood flow and conduction, exclusively at the expense of the arteriovenous anastomotic fraction as the capillary fraction did in fact increase. The highest dose (300 microg kg(-1)) produced a reduction of 52+/-6% from the baseline arteriovenous anastomotic flow. When carotid haemodynamic changes after a single 100 microg kg(-1)dose of BMS-181885 or sumatriptan were studied at different time-points, BMS-188185 had a longer duration of action. Both BMS-181885 (pD2:7.9+/-0.1; Emax:9+/-3% of the contraction to 100 mM K+) and sumatriptan (pD2:6.3+/-0.1; Emax:28+/-8% of the contraction to 100 mM K+) contracted the human isolated coronary artery. The above results suggest that (i) the longer-lasting vasoconstrictor action of BMS-181885 on porcine carotid arteriovenous anastomoses may be related to its reported slow dissociation from 5-HT1B/1D receptor, and (ii) BMS-181885 should be able to abort migraine headaches in patients. It will be interesting to find out whether these properties are clinically important so that the drug exhibits less headache recurrence and coronary side-effects than sumatriptan.

Animals↗
PubMed1997

Prorenin, renin, angiotensinogen, and angiotensin-converting enzyme in normal and failing human hearts. Evidence for renin binding.

BACKGROUND: A local renin-angiotensin system in the heart is often invoked to explain the beneficial effects of ACE inhibitors in heart failure. The heart, however, produces little or no renin under normal conditions. METHODS AND RESULTS: We compared the cardiac tissue levels of renin-angiotensin system components in 10 potential heart donors who died of noncardiac disorders and 10 subjects with dilated cardiomyopathy (DCM) who underwent cardiac transplantation. Cardiac levels of renin and prorenin in DCM patients were higher than in the donors. The cardiac and plasma levels of renin in DCM were positively correlated, and extrapolation of the regression line to normal plasma levels yielded a tissue level close to that measured in the donor hearts. The cardiac tissue-to-plasma concentration (T/P) ratios for renin and prorenin were threefold the ratio for albumin, which indicates that the tissue levels were too high to be accounted for by admixture with blood and diffusion into the interstitial fluid. Cell membranes from porcine cardiac tissue bound porcine renin with high affinity. The T/P ratio for ACE, which is membrane bound, was fivefold the ratio for albumin. Cardiac angiotensinogen was lower in DCM patients than in the donors, and its T/P ratio was half that for albumin, which is compatible with substrate consumption by cardiac renin. CONCLUSIONS: These data in patients with heart failure support the concept of local angiotensin production in the heart by renin that is taken up from the circulation. Membrane binding may be part of the uptake process.

Adolescent↗
PubMed1997

Effects of avitriptan, a new 5-HT 1B/1D receptor agonist, in experimental models predictive of antimigraine activity and coronary side-effect potential.

Several acutely acting antimigraine drugs, including ergotamine and sumatriptan, have the ability to constrict porcine arteriovenous anastomoses as well as the human isolated coronary artery. These two experimental models seem to serve as indicators, respectively, for the therapeutic and coronary side-effect potential of the compounds. Using these two models, we have now investigated the effects of avitriptan (BMS-180048; 3-[3-[4-(5-methoxy-4-pyrimidinyl)-l-piperazinyl[propyl]-N-methyl-l H-indole-5-methane-sulfonamide monofumarate), a new 5-HT 1B/1D receptor agonist. In anaesthetized pigs, avitriptan (10, 30, 100 and 300 micrograms.kg-1) decreased the total carotid blood flow by exclusively decreasing arteriovenous anastomotic blood flow; capillary blood flow was increased. The mean +/- SEM i.v. dose of avitriptan eliciting a 50% decrease (ED50) in the porcine carotid arteriovenous anastomotic blood flow was calculated to be 76 +/- 23 micrograms.kg-1 (132 +/- 40 nmol.kg-1) and the highest dose (300 micrograms.kg-1) produced a 72 +/- 4% reduction. In recent comparative experiments (DeVries et al. 1996), the mean +/- SEM ED50 (i.v.) of sumatriptan in decreasing carotid arteriovenous anastomotic blood flow was 63 +/- 17 micrograms.kg-1 (158 +/- 43 nmol.kg-1), with a reduction of 76 +/- 4% by 300 micrograms.kg-1, i.v. Both avitriptan (pD2; 7.39 +/- 0.09; Emax: 13.0 +/- 4.5% of the contraction to 100 mM K+) and sumatriptan (pD2: 6.33 +/- 0.09; Emax: 15.5 +/- 2.3% of the contraction to 100 mM K+) contracted the human isolated coronary artery. The above results suggest that avitriptan should be able to abort migraine headaches in patients, but may exhibit sumatriptan-like effects on coronary arteries. Initial clinical studies have demonstrated the therapeutic action of the drug in acute migraine.

Animals↗
PubMed1997

Effects of cryopreservation on contractile properties of porcine isolated aortic valve leaflets and aortic wall.

Human semilunar donor heart valves can be stored in banks, awaiting transplantation. To evaluate the result of the preservation protocols, a quantitative description of the tissue is necessary. In this study we investigated in a quantitative way the contractile properties of fresh and cryopreserved porcine isolated aortic heart valve leaflets in response to a number of endogenous vasoactive compounds. The responses of strips of the aortic wall were included for comparison. Contraction was measured isometrically in response to potassium (K+; 100 mmol/L), 5-hydroxytryptamine (1 nmol/L to 100 micromol/L), noradrenaline (1 nmol/L to 100 micromol/L), endothelin-1 (0.01 nmol/L to 0.3 micromol/L), and prostaglandin F(2alpha) (0.1 nmol/L to 10 micromol/L). The pharmacologic parameters E(MAX) (the maximal response expressed as a percentage of contraction to a 100 mmol/L dose of K+) and EC50 (the concentration that produces 50% of the maximal effect) were calculated for every compound (n = 6 to 7 each). We observed that all specimens contracted in response to potassium. Its magnitude in fresh leaflets equaled 1.6 +/- 0.14 mN compared with 26.6 +/- 2.6 mN in fresh aortic wall. Noradrenaline, endothelin-1, and prostaglandin F(2alpha) all caused contraction in valvular leaflets and aortic wall, whereas 5-hydroxytryptamine caused contraction in the valvular leaflets but relaxation in aortic wall. After cryopreservation, the response to K+ amounted to 24% of the response of the fresh specimens in valvular leaflets (n = 25) and 14% in aortic wall (n = 26). The values of E(MAX) and EC50 of the responses to noradrenaline, endothelin-1, and prostaglandin F(2alpha) remained unchanged. Although the physiologic relevance of contraction of valvular leaflets needs further study, its measurement may provide an additional model to verify the consequences of alternative methods of preservation.

Animals↗
PubMed1996

Investigations with GMC2021 in experimental models predictive of antimigraine activity and coronary side-effect potential.

Several acutely acting antimigraine drugs, including sumatriptan and other second generation 5-HT1D receptor agonists, have the ability to constrict porcine carotid arteriovenous anastomoses as well as the human isolated coronary artery. These two experimental models seem to serve as indicators, respectively, for the therapeutic and coronary side-effect potential of the compounds. Using these two models, we have now investigated the effects of GMC2021 (3-[2-(dimethylanimo)ethyl]-5-[(trifluoromethyl)sulfonyl]oxy][1 H]indole oxalate, a close analogue of sumatriptan. GMC2021 (30, 100, 300 and 1000 micrograms.kg-1, i.v.) decreased the total carotid blood flow by exclusively decreasing arteriovenous anastomotic blood flow; capillary blood flow to the skin and ears was moderately increased. The mean +/- S.E.M. dose of GMC2021 eliciting a 50% decrease (ED50) in the porcine carotid arteriovenous anastomotic blood flow was found to be 1.1 +/- 0.3 mumol.kg-1 and the highest dose (1000 micrograms.kg-1) produced a 67 +/- 4% reduction. The carotid haemodynamic effects of GMC2021 were reduced by the selective 5-HT1D receptor antagonist, GR127935 (N-[methoxy-3-(4-methyl-1- piperazinyl)phenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)[1 , 1-biphenyl]-4-carboxamide hydrochloride), which completely antagonizes porcine carotid haemodynamic responses to sumatriptan (ED50: 0.16 mumol.kg-1, i.v.). Compared to sumatriptan (pD2: 6.12 +/- 0.15; Emax: 31.3 +/- 12.3% of contractions to 100 mM K+), GMC2021 was less potent in constricting the human isolated coronary artery (pD2: 5.45 +/- 0.2; Emax: 21.0 +/- 4.8% of contractions to 100 mM K+). The above results suggest that GMC2021 constricts carotid arteriovenous anastomoses partly by a 5-HT1D receptor and partly by another, probably novel, receptor and that GMC2021 should be able to abort migraine headaches in patients, with perhaps a less propensity for coronary side effects.

Animals↗
PubMed1996

Augmented contraction of the human isolated coronary artery by sumatriptan: a possible role for endogenous thromboxane.

1. The antimigraine drug, sumatriptan, contracts the human coronary artery and, in some patients, elicits chest symptoms (e.g. pressure and pain), particularly after subcutaneous administration. We studied the effects of the thromboxane A2 (TxA2) analogue, U46619 and endothelin-1 on contractile responses to sumatriptan in the human isolated coronary artery as well as the role of endogenously produced TxA2 and endothelin-1 in contractions evoked by sumatriptan. 2. In the presence of U46619 (1 and 3 nM), mean concentration-response curves to sumatriptan in the human coronary artery were shifted vertically due to the initial contraction by U46619, but when this initial contraction was subtracted from the response to sumatriptan, no significant augmentation was observed. However, analysis of the degree of augmentation in individual arterial segments revealed that the augmentation was variable and related inversely to the Emax of sumatriptan in the absence of U46619 (r = 0.78 and 0.81 for 1 and 3 nM, respectively; P < 0.05). 3. Treatment with the TxA2 receptor antagonist, SQ30741 (100 nM), or incubation of vessel segments with aspirin (10 microM), significantly reduced responses to sumatriptan; in aspirin-treated vessel segments, SQ30741 failed to decrease further the contractions to sumatriptan. The decrease in Emax of sumatriptan by both SQ30741 and aspirin correlated significantly with the Emax of sumatriptan without SQ30741 (r = 0.74; P < 0.01) or aspirin (r = 0.94; P < 0.01). In aspirin-treated vessel segments, responses to sumatriptan were significantly augmented in the presence of U46619 (3 nM; P < 0.05). 4. The specificity of SQ30741 was demonstrated by its ability to antagonize coronary artery contractions to U46619 (pA2: 7.54 +/- 0.30), but not endothelin-1. Similarly, incubation with aspirin (10 microM) did not affect contractile responses to endothelin-1, but significantly reduced TxA2 production in coronary artery segments as judged by a decrease in thromboxane B2 (TxB2) from 4.77 +/- 0.98 to 1.38 +/- 0.36 ng g-1 2 h-1. 5. Endothelin-1 (1 nM) did not significantly augment contractions to sumatriptan; there was also no relationship between the degree of augmentation and the control Emax of sumatriptan in the absence of endothelin-1. Furthermore, unlike SQ30741 or aspirin, a high concentration (100 nM) of the non-selective ETA/ETB receptor antagonist, SB 209670, failed to affect contractile responses to sumatriptan. However, SB 209670 potently antagonized coronary artery contractions induced by endothelin-1 with a pA2 of 8.84 +/- 0.32. 6. Compared to control vascular segments, endothelial denudation did not reduce TxA2 production (with endothelium = 2.56 +/- 1.38 vs. without endothelium = 12.32 +/- 4.94 ng TxB2 g-1 2 h-1), suggesting that the production of TxA2 is not confined to the endothelium. The sumatriptan-induced contractions were also unaffected by endothelial denudation. 7. The results of the present study suggest that endogenously produced TxA2 enhances contractions to sumatriptan in the human isolated coronary artery. Such a mechanism may play a role in causing chest symptoms after sumatriptan by potentiating coronary vascular contraction by sumatriptan in vivo.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

[Arg8]vasopressin-induced responses of the human isolated coronary artery: effects of non-peptide receptor antagonists.

Contractions induced by [Arg8]vasopressin (vasopressin) and the effect of nonpeptide vasopressin receptor antagonists were studied in the human isolated coronary artery. Vasopressin induced contraction of coronary artery segments with a high pD2 (9.25) but a low Emax (11.8% of the response to 100 mM K+). This response was not affected by removal of the endothelium. Contraction was antagonized by the vasopressin V1 receptor antagonist SR 49059 ((2S) 1-[(2R 3S)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene- sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2- carboxamide) (pA2: 9.76). OPC-31260 ([5-dimethylamino-1-(4-(2-methylbenzoylamino)benzoyl)-2,3,4,5-tetr ahydro-1H- benzazepine]: vasopressin V2 receptor antagonist) and OPC-21268 (1-(1-[4-(3-acetylaminopropoxy) benzoyl]-4-piperidyl)-3,4- dihydro-2(1H)-quinolinone: reported vasopressin V1 receptor antagonist) were less potent antagonists of vasopressin-induced contractions (pA2: 7.31 and 5.6, respectively). The antagonist potency order (SR 49059 > OPC-31260 > OPC-21268) corresponds to the reported affinity order for the human cloned vasopressin V1 receptor. Therefore, the vasopressin V1 receptor antagonist SR 49059, but not OPC-21268, appears to be an appropriate tool to investigate further the role of vasopressin in pathological processes involving coronary vasoconstriction in humans.

Adolescent↗
PubMed1995

Angiotensin-converting enzyme in the human heart. Effect of the deletion/insertion polymorphism.

BACKGROUND: An insertion (I)/deletion (D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been associated with differences in the plasma levels of ACE as well as with myocardial infarction, cardiomyopathy, left ventricular hypertrophy, and coronary artery disease. METHODS AND RESULTS: We determined the cardiac ACE activity and the ACE genotype in 71 subjects who died of noncardiac disorders. Cardiac ACE activity was significantly higher (P < .01) in subjects with the ACE DD genotype (12.7 +/- 1.9 mU/g wet wt) compared with subjects with the ID (8.7 +/- 0.8 mU/g) and the II (9.1 +/- 1.0 mU/g) genotypes. This difference was independent of sex, age, and the time required for tissue collection. CONCLUSIONS: Cardiac ACE activity is highest in subjects with the DD genotype. Elevated cardiac ACE activity in these subjects may result in increased cardiac angiotensin II levels, and this may be a mechanism underlying the reported association between the ACE deletion polymorphism and the increased risk for several cardiovascular disorders.

Adolescent↗
PubMed1994

The current endothelin receptor classification: time for reconsideration?

The possible involvement of endothelins in a variety of diseases has attracted the attention of many pharmacologists in search of a novel therapeutic approach. The rapid development of endothelin research has resulted in the molecular characterization and pharmacological recognition of ETA and ETB receptors, and in the development of compounds selective for these receptors. However, the characterization of receptors in various assays has shown that a number of effects are mediated by receptors that do not fit the present criteria for ETA or ETB receptors. In this article, Willem Bax and Pramod Saxena address endothelin receptors in general, and atypical receptors in particular.

Amino Acid Sequence↗
PubMed1994

Different endothelin receptors involved in endothelin-1- and sarafotoxin S6B-induced contractions of the human isolated coronary artery.

1. Endothelin receptors, that mediate contraction of the human isolated coronary artery, were characterized by use of a number of agonists and antagonists. Contraction induced by the non-selective agonists, endothelin (ET)-1 and sarafotoxin S6b, was compared in endothelium-intact and endothelium-denuded ring segments. The effects of ET-1 and BQ-123 (an ETA receptor antagonist) were investigated both in ring segments and in spirally cut strips. Lastly, the effect of phosphoramidon was studied on contraction induced by big-ET-1. 2. The order of agonist potency (pD2) in endothelium-intact coronary artery ring segments was: ET-1 (8.27) approximately sarafotoxin S6b (8.16) > big-ET-1 (< 7.1) approximately ET-3 (< 6.9). [Ala1,3,11,15]ET-1 (ETB receptor agonist) caused significant contraction only at 1 microM, whereas 0.3 microM big-ET-3 had no effect. Removal of the endothelium in ring segments did not affect the contractile response to ET-1 or to sarafotoxin S6b. 3. After a full concentration-response curve had been obtained to ET-1 or sarafotoxin S6b, further contractions of the endothelium-intact coronary artery segments could only be achieved by applying ET-1 in segments exposed to sarafotoxin S6b, and not the reverse. 4. BQ-123 (0.1 microM) antagonized contractions of endothelium-intact ring segments induced by sarafotoxin S6b (pKB 7.86). Only 10 microM BQ-123 antagonized contractions induced by ET-1 (pKB 5.75). FR139317 was also more potent against sarafotoxin S6b (pKB 8.24-8.47) than against ET-1 (pKB 6.11). [Ala1,3,11,15]ET-1 (1 microM) had no effect on the contractile response to ET-1 or to sarafotoxin S6b. 5. In strip preparations with intact endothelium, the pD2 of ET-l increased to 9.04 =/- 0.16 (vs.8.50 +/- 0.07 in rings), and BQ-123 (1 microM) caused a rightward shift of the ET-l induced concentration response curve (pKB 6.62 vs. 5.75 in rings).6. Contractile responses to big-ET-1 of endothelium-intact coronary artery segments were attenuated in the presence of phosphoramidon (100 microM), indicating conversion of big-ET-1 to ET-1 within the coronary artery segment.7. The present study indicates that ET-1 and sarafotoxin S6b contract the human isolated coronary artery via different receptors, which can probably be best characterized as subtypes of the ETA receptor.Furthermore, it is demonstrated that the type of preparation (ring or strip) may affect the potency of ET-1 as an agonist and of BQ-123 as an antagonist.

Adolescent↗
PubMed1994

Low-dose aspirin inhibits platelet-induced contraction of the human isolated coronary artery. A role for additional 5-hydroxytryptamine receptor antagonism against coronary vasospasm?

BACKGROUND: The beneficial effect of low-dose aspirin in the prevention of coronary vasospasm is well documented. In this study, we investigated the contractile effect of human washed platelets on the human isolated coronary artery. We concentrated on the effect of low-dose aspirin (40 mg/d) taken by the platelet donor and on the efficacy of thromboxane A2 (TXA2) and 5-hydroxytryptamine (5-HT) receptor antagonists. METHODS AND RESULTS: Human coronary artery segments were suspended in an organ bath set-up for isometric tension measurement. Platelets (10(9) to 3 x 10(10)/L) elicited concentration-dependent contractile responses of the coronary artery segments, reaching 28.4 +/- 7.1% of contractions induced by 100 mmol/L K+. The contractile response tended to be decreased in vessel segments with histological signs of early atherosclerosis. Contraction was significantly attenuated after pretreatment of the vessel segments with ketanserin (5-HT2 receptor antagonist, 1 mumol/L) or SQ30741 (TXA2 receptor antagonist, 0.01 mumol/L), reaching 8.8 +/- 2.3% and 3.2 +/- 2.2% of contraction to 100 mmol/L K+, respectively. Platelets obtained from the same platelet donors after they had taken aspirin (40 mg/d for 7 to 13 days) caused significantly lower contractile responses (7.6 +/- 2.7% of 100 mmol/L K+) associated with an almost selective inhibition of the synthesis of thromboxane measured in the organ bath solution (untreated platelets, 2.19 +/- 0.43 nmol/L; aspirin-treated platelets, 0.66 +/- 0.05 nmol/L). The amount of 5-HT secreted in the organ bath remained unaltered (65.17 +/- 9.94 and 64.03 +/- 8.98 nmol/L, respectively). This explains why ketanserin significantly attenuated the residual contractile responses caused by platelets obtained from aspirin-treated subjects, whereas SQ30741 caused minor, nonsignificant additional attenuation. CONCLUSIONS: The results of the present study therefore suggest that additional antagonism of the contractile 5-HT receptors in the coronary artery may increase the efficacy of low-dose aspirin in vivo.

Adolescent↗
PubMed1993

5-HT receptors mediating contractions of the isolated human coronary artery.

We investigated contractile responses of the isolated human coronary artery to 5-hydroxytryptamine (5-HT), washed human platelets, sumatriptan and ergotamine. 5-HT (pD2: 6.8 +/- 0.1, Emax: 47.7 +/- 6.8 mN) and platelets (effect 14.4 +/- 2.8 mN with 3.10(10) platelets/l) caused contractile responses which were attenuated by ketanserin (1 microM). In the presence of ketanserin (1 microM), both rauwolscine (1 and 10 microM) and cyanopindolol (1 and 10 microM) caused concentration-dependent additional antagonism against contractions induced by low (< or = 1 microM) concentrations of 5-HT. Sumatriptan-induced contractions (pD2: 6.2 +/- 0.1; Emax: 10.7 +/- 2.4 mN) were antagonized to a similar extent by both rauwolscine (1 microM) and cyanopindolol (1 microM) (pKB: 6.5 +/- 0.1 and 6.4 +/- 0.1, respectively) and also by metergoline (0.1 microM; pKB: 7.2 +/- 0.1). The order of potency of antagonists against sumatriptan resembles the order reported for the human saphenous vein 5-HT1D-like receptor. No significant additional antagonism by cyanopindolol (1 microM) or rauwolscine (1 microM) against platelet-induced contractile responses was observed. Ergotamine caused potent contractile responses (pD2: 8.4 +/- 0.3, Emax: 19.4 +/- 2.4 mN). It is concluded that although 5-HT2 receptors predominantly mediate 5-HT-induced contractions, the 5-HT1-like receptor seems to play a role in coronary vasospasm caused by low concentrations of 5-HT.

Adolescent↗
PubMed1993

Heterogeneity of endothelin/sarafotoxin receptors mediating contraction of the human isolated saphenous vein.

We investigated the effect of the ETA receptor antagonist, BQ-123 (0.1 and 1 microM), on contraction of the human isolated saphenous vein induced by endothelin-1 or sarafotoxin S6b. Contraction in response to endothelin-1 was not affected by BQ-123. In contrast, BQ-123 biphasically attenuated the contractions due to sarafotoxin S6b. These data indicate that (i) endothelin-1 induces contractions of the human saphenous vein via a non-ETA receptor and (ii) contractions in response to sarafotoxin S6b are mediated in part via a receptor different from the receptor mediating contraction due to endothelin-1.

Aged↗