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Influence of nifedipine on vascular reactivity: studies in the isolated perfused rat kidney.

In order to elucidate the mechanisms involved in the antihypertensive action of the calcium-antagonist nifedipine, experiments were carried out in the isolated rat kidney, perfused with a blood-free medium containing 1.80mM Ca++. The renal vasoconstrictor effects of bolus injections ofnoradrenaline (NA, 40–60 ng) and angiotensin II (AT II, 2.5, 5,10 ng) was assessed before and during perfusion of nifedipine (10−9–10−8M). At a concentration of 10−8M, nifedipine significantly blunted

(1) the pressor response to 40 and 60 ng of NA by 57±5 and 54 ± 7%, respectively;

(2) the pressor response to 5 and 10 ng of AT II by 60 ±7 and 73 ±9%, respectively. Since nifedipine inhibits NA and AT II pressor activity at a concentration close to that achieved in man during treatment by this agent, this mechanism is likely to be involved in the antihypertensive effect of nifedipine.