Effects of vasodilator antihypertensive agents on renal function

The effects of calcium antagonist and noncalcium antagonist vasodilator antihypertensive agents were examined using renal clearance, hemodynamic, and micropuncture techniques in anesthetized normotensive dogs, rats, and conscious spontaneously hypertensive rats. At doses that either failed to affect mean arterial pressure or lowered it equally, the calcium antagonist vasodilator agents nifedipine and felodipine produced a natriuresis and renal vasodilatation whereas the noncalcium antagonist vasodilator agents hydralazine and minoxidil produced an antinatriuresis and renal vasoconstriction. These findings support the view that the development of tolerance to the antihypertensive effect of noncalcium antagonist vasodilators, which is usually reversed by concomitant diuretic administration, is dependent on renal sodium and water retention. In addition, the capacity of calcium antagonist vasodilators to directly inhibit renal tubular sodium reabsorption explains their natriuretic action and the absence of antinatriuresis may contribute to lesser development of tolerance.