ABSTRACT
To investigate the role of calcium in angiotensin II (A II) induced contractions in rabbit aortic strip, the action of verapamil, nifedipine, cinnarizine and saralasin was studied. The cumulative dose response curves obtained with A II shifted to right with increasing concentrations of all these four agents. The antagonism was noncompetitive. The pD'2 value of saralasin was 8.49 of nifedipine, 8.15 and or verapamil 7.92. Cinnarizine which mainly acts at intracellular site had pD'2 value 5.54. The results indicate that A II induced contractions critically depend on entry of calcium through channels which appear to be closely associated with angiotensin receptors.
Subject(s)
Angiotensin II/antagonists & inhibitors , Animals , Calcium Channel Blockers/pharmacology , Female , Male , Rabbits , Saralasin/pharmacology , Vasoconstriction/drug effectsABSTRACT
The effect of verapamil on pressor response to Angiotensin II (A II) was investigated in rats. The responses to A II (10, 20, 40 ng, iv) was reduced after verapamil (50 and 100 micrograms, iv per rat) in a dose dependent manner. Treatment for 5 day with verapamil (18 mg/100 g/day, po) let to some reduction in basal blood pressure but pressor response to A II was not changed. Treatment for 20 days significantly reduced the basal blood pressure and increased the responsiveness to A II. it is concluded that Ca++ plays a major role in the pressor responses to A II and that chronic treatment with verapamil may reduce basal blood pressure.