Calcium entry blocker nicardipine inhibits sodium and inorganic phosphate reabsorption independent of renal circulation in dogs.

The effects of nicardipine on renal function were studied in anesthetized dogs. The changes in the tubular sodium (Na) and inorganic phosphate (PO(4)) reabsorption caused by the drug infusion into the renal artery without altered systemic and real circulation were especially evaluated. In dogs receiving a smaller dose of nicardipine (5 ng.kg(-1).min(-1)) into the left renal artery the blood pressure and renal circulation did not change, but urine volume and urinary Na and PO(4) excretion increased significantly. In dogs receiving a larger dose of nicardipine (50 ng.kg(-1).min(-1)) into the renal artery, renal plasma flow, urine volume and urinary Na and PO(4) excretion increased significantly, but creatinine clearance did not. The fractional distal Na reabsorption did not change with nicardipine infusion in either group. PO(4) reabsorption is considered to occur mainly in the proximal renal tubule, so its appearance in urine in increased quantities without the changes of systemic and renal circulation suggests proximal activity of the drug.