Effect of verapamil on renal vasoconstriction induced by angiotensin II, norepinephrine or renal nerve stimulation in anesthetized dogs.

The effect of verapamil on the decrease in renal blood flow (RBF) induced by angiotensin II (Ang II), norepinephrine (NE) or renal nerve stimulation (RNS) was examined in pentobarbital-anesthetized dogs. The injection into the renal artery of Ang II (0.01-0.1 micrograms), or NE (0.1-1.0 micrograms), or RNS (1-10 Hz) decreased RBF in a dose- or frequency-dependent manner. The renal arterial infusion of verapamil (30 micrograms/min followed by 100 micrograms/min) brought about a sustained increase in RBF and inhibition of renal vasoconstriction induced by Ang II or NE, but not by RNS, when the extent of vasoconstriction was estimated in terms of absolute changes in RBF. We also observed that the inhibitory effect of verapamil on Ang II-induced vasoconstriction was greater than on NE-induced constriction, as estimated from the % change in RBF. These results indicate that in canine renal vasculature, verapamil exerts different inhibitory effects on the vasoconstriction induced by Ang II, NE or RNS.