Calcium antagonistic effects of compound D 600 on renal tubular reabsorption

Effects of Verapamil and Nifedipine on Renal Function and Hemodynamics in the Dog

“…Usually increments of 10-85% in GFR in the dog induce little change in uri nary calcium and sodium excretion, imply ing a compensatory increase in tubular reab sorption of these ions [22], In contrast, renal vasodilatation with acetylcholine and bradykinin causes parallel increases in sodium and calcium clearances by inhibiting tubular reabsorption of these ions [17], Thus, part of the calcium losses in this study may be asso ciated with the vasodilatation or with the solute diuresis observed with calcium block ers [37]. Finally, a direct effect of calcium blockers on tubular calcium transport seems unlikely since compound D-600, a methoxy derivative of verapamil, has no direct effect when applied to the lumen of the proximal tubule in the rat [16], Potassium excretion and the fractional excretion of potassium were markedly en hanced by the calcium blockers. The most likely explanation for the rise in potassium excretion must be the rate of sodium deliv ery to the distal nephron [12], This is sup ported by the observation of a parallel rise in urine flow rate, sodium and potassium ex cretion, and the calculated fractional distal delivery.…”