Antihypertensive and renal vasodilator effect of diltiazem in DOCA-salt hypertensive dog.

We studied the effect of an intravenous (i.v.) infusion of diltiazem (15 micrograms/kg/min) given for 1 week on several cardiovascular parameters, renal blood flow, and electrolyte and urinary excretion in chronically instrumented DOCA-salt hypertensive dogs. On the first recording session, 24 h after diltiazem infusion was started, arterial blood pressure was decreased and renal blood flow was increased by 36%. Thereafter, the blood pressure reached a normotensive level and remained at that level for the duration of the infusion in all but one dog in which the dose had to be increased on day 7. Renal blood flow was increased for 3 days and then tended to return toward control at the end of the infusion period. An increase in urine output was seen during the period of drug infusion, but no increase in sodium excretion was detected. Pressor and renal blood flow responses to norepinephrine (NE), phenylephrine, and angiotensin II were evoked before and on the last day of the diltiazem infusion. The decreases in renal blood flow produced by all three agonists and the pressor response to NE were reduced by diltiazem. These results indicate that this calcium entry blocker can reestablish blood pressure to a normotensive level in DOCA-salt--treated dogs, but that the renal vasodilator effect accompanying the blood pressure decrease is not consistently sustained.