Vasoconstrictor agonists activate G-protein-dependent receptor-operated calcium channels in pig aortic microsomes.
Receptor-operated Ca2+ channels were characterized by their ability to decrease steady-state ATP-dependent Ca2+ accumulation into pig aortic microsomes. The vasoconstrictor agents noradrenaline, angiotensin II and adenosine 5'-[alpha beta-methylene]triphosphate (pp[CH2]pA) all decreased Ca2+ accumulation only when sonicated into vesicles (to allow access to receptor sites) and in the presence of guanosine 5'-[beta gamma-imido]triphosphate to activate transducing G-proteins. The effect of noradrenaline was inhibited by the alpha 2 antagonist yohimbine, but not by the alpha 1 antagonist prazosin. The effect of none of the agonists was reversed by diltiazem. SK&F 96365 (an inhibitor of receptor-mediated Ca2+ influx into intact cells) reversed the effect of noradrenaline, but not that of pp[CH2]pA, which suggests that at least two receptor-operated channels may be present in this preparation.
Blayney
L M
LM
Department of Cardiology, University of Wales College of Medicine, Heath Park, Cardiff, U.K.
Gapper
P W
PW
Newby
A C
AC
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D003000:Clonidine / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008861:Microsomes / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D000317:Adrenergic alpha-Antagonists; D015220:Calcium Channels; D007093:Imidazoles; D011942:Receptors, Adrenergic, alpha; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D006165:Guanylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins; D004110:Diltiazem; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D003000:Clonidine; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium; D009638:Norepinephrine