Comparative renal effects of calcium channel blockers in conscious spontaneously hypertensive rats

Five calcium channel blockers with diverse chemical structures were studied for potential renal selectivity after oral administration of a single dose to conscious spontaneously hypertensive rats. Nitrendipine (3 and 10 mg/kg) and diltiazem (30 and 100 mg/kg) caused significant increases in sodium and water excretion. In comparison, prenylamine (100 and 300 mg/kg) and flunarizine (100 and 300 mg/kg) failed to augment sodium and water excretion. Verapamil caused significant natriuresis only at 30 mg/kg. These data suggest that the diuretic and natriuretic action is not a common property of all calcium channel blockers. Pretreatment with SCH 23390 (20 mg/kg), a dopamine DA1 antagonist, selectively attenuated the diuresis and natriuresis induced by high doses of diltiazem (100 mg/kg) and nitrendipine (10 mg/kg) without blocking the renal responses to hydrochlorothiazide (1 mg/kg). Similarly, reserpinization abolished the renal but not the hypotensive action of diltiazem. Pretreatment with indomethacin (10 mg/kg), a cyclooxygenase inhibitor also significantly attenuated the diuresis and natriuresis elicited by diltiazem (100 mg/kg). These data suggest that intact dopamine and prostaglandin systems in the kidney are required for optimal expression of the renal effects of diltiazem and nitrendipine.