[Effect of nifedipine on renal activity]

Sublingual administration of nifedipine (N) at a dose of 20 mg to 8 persons without cardiovascular and renal pathology and to 19 patients with congestive heart failure (CHF) increased renal excretion of sodium (by an average of 51.1-132.8%), water (by an average of 31.7-101.9%), potassium (by an average of 43.2-63.2%) and calcium (by an average of 118%). The natriuretic effect of N appeared in 20 min reaching its maximum in 45-60 min, being more noticeable in CHF. An increment of natriuresis resulted from a decrease in sodium tubular reabsorption (correlation factor--0.92) rather than from an increase in glomerular filtration (correlation factor +0.50). N suppressed sodium reabsorption in the proximal tubule (by an average of 34.1%) as well as in the segment, more distal of Henle's loop (by an average of 6.8%). N might suppress directly calcium-dependent mechanisms of sodium transtubular transport but it could also produce a mediated effect as a result of shifts of renal hemodynamics.