Inhibitory effects of cadralazine and its metabolite, ISF-2405, on contractions and the level of cytosolic Ca2+ in vascular smooth muscle.
The inhibitory effects of a hypotensive agent, cadralazine and its metabolite, ISF-2405, on the level of cytosolic Ca2+ ([Ca2+]cyt) and on contractions were examined in isolated vascular smooth muscle. Cadralazine slightly inhibited the transient norepinephrine-induced contraction in rabbit aorta and canine femoral, renal and mesenteric arteries and saphenous vein, and prostaglandin F2 alpha-induced contractions in canine basilar and coronary arteries. In contrast, ISF-2405 inhibited the contractions induced by prostaglandin F2 alpha in canine basilar and coronary arteries and those induced by norepinephrine in canine renal and femoral arteries and rabbit aorta. In aorta, ISF-2405 inhibited the increase in [Ca2+]cyt and muscle tension caused by norepinephrine. A Ca2+ channel blocker, verapamil, inhibited the norepinephrine-stimulated increase in [Ca2+]cyt more potently than it inhibited the increase in muscle tension, and ISF-2405 inhibited the verapamil-resistant part of the contraction. In Ca2(+)-free solution, norepinephrine induced transient increases in [Ca2+]cyt and muscle tension. ISF-2405 inhibited these changes. However, ISF-2405 did not inhibit the transient contraction induced by caffeine in the aorta. These results suggest that cadralazine is metabolized to ISF-2405 and inhibits vascular smooth muscle contraction by inhibiting receptor-mediated Ca2+ influx, Ca2+ release and Ca2+ sensitization of contractile elements.
Mitsui
M
M
Department of Veterinary Pharmacology, Faculty of Agriculture, University of Tokyo, Japan.
Nakao
K
K
Inukai
T
T
Karaki
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011724:Pyridazines / Q000494:pharmacology*; D011817:Rabbits; D014665:Vasodilator Agents / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology
D011724:Pyridazines; D014665:Vasodilator Agents; C055809:ISF 2405; C031877:cadralazine; D015237:Dinoprost; D014700:Verapamil; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine