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[Sar1,Phe(Br5)8] angiotensin II (Br5Ang II) is a specific, quasi-irreversible antagonist of angiotensin II (Ang II) in vitro. In vivo, this compound is a very potent, Ang II-specific antagonist with a very long duration of action against Ang II-induced blood pressure (BP) increases. In the "low-sodium" dog, this compound induces a prolonged BP reduction(More)
We investigated the dependence upon extracellular Ca2+ of contractile responses of the isolated rabbit main pulmonary artery to the alpha-adrenoceptor subtype-selective agonists clonidine (alpha 2) and methoxamine (alpha 1). The calcium-entry blocker verapamil caused a weak, surmountable antagonism of contractile responses to methoxamine, whereas the(More)
Ro 40-5967 is a structurally novel Ca2+ channel blocker which binds to the verapamil-type receptor of cardiac membranes. Its biological activity was investigated in comparison with verapamil in isolated vascular, cardiac, and gastrointestinal muscle preparations, as well as in isolated perfused hearts. Ro 40-5967 was more potent in increasing coronary(More)
The cardiotonic agent DPI 201-106 was investigated for its effects on (a) contractile force in guinea pig left atria, (b) membrane currents in isolated guinea pig cardiac myocytes, and (c) [3H]nitrendipine binding in guinea pig cardiac membranes. The compound elicited a positive inotropic effect in normally polarized (5.9 mM extracellular KCl) and a(More)
We investigated the possible mechanisms involved in the positive inotropic activity of Ro 13-6438 (R-6-chloro-1,5-dihydro-3- methylimidazo -[2,1-b] quinazolin -2[ 3H]-one), a structurally novel cardiotonic agent with vasodilating properties. The positive inotropic response to Ro 13-6438 of the isolated guinea pig papillary muscle was accompanied by(More)
A specific, high affinity (KD 1.8 nM) binding site for the calcium entry blocking drug [3H]nifedipine was identified in homogenates of rabbit myocardium. [3H]Nifedipine binding was rapid (t1/2 3 min) and reversible (t1/2 11 min). Calcium entry blockers with different chemical structures competed with [3H]nifedipine binding in the potency order: nifedipine(More)
The demonstrated proportionality between norepinephrine and dopamine-beta-hydroxylase released exocytotically from sympathetic nerve endings led us to explore the possible physiologic significance attached to this proportionality. The beta adrenoreceptor mediated desensitization of the hyperpolarization response to norepinephrine observed in pinealocyte(More)
Cibenzoline, a class 1 (local anaesthetic-type) antiarrhythmic drug, was investigated for possible effects upon the myocardial Ca2+ inward current. In voltage-clamp experiments with isolated cardiac myocytes of guinea-pig, cibenzoline caused a concentration-dependent inhibition of the Ca2+ current, with an IC50 of 14 microM. Inhibition of the Ca2+ current(More)
Adenosine and adenosine 5'-monophosphate (AMP) augment contractile responses to norepinephrine (NE) in isolated guinea-pig vas deferens. Dipyridamole slightly enhances, while theophylline antagonizes, adenosine effects on responses to NE. Adenosine triphosphate (ATP) and the nonhydrolyzable analog, adenosine 5'-(beta,gamma-imido)triphosphate (AppNp) depress(More)
The binding characteristics and pharmacological properties of o-isothiocyanate dihydropyridine [oNCS-DHP; 2,6-dimethyl-3,5-dicarbomethoxy-4-(2-isothiocyanatophenyl)-1, 4-dihydropyridine] were investigated in guinea pig heart and ileum. [3H]oNCS-DHP bound to a single population of high-affinity sites (Bmax = 107 fmol/mg of protein and Kd = 0.99 nM) in(More)