Effect of nitrendipine on urine volume, osmolality, and electrolyte excretion in normal, adrenal-enucleate, and...

Female Sprague-Dawley rats were sham operated, adrenal-enucleated, or mononephrectomized. Half of each group received 30 mg/kg of nitrendipine; the remainder were given equal volumes of vehicle, and all rats were then injected i.p. with 40 ml/kg of 0.9% NaCl solution. Urine was collected over a 6-h period. Nitrendipine-treated intact rats excreted slightly more water and Na+ and less K+ than controls, but none of the differences were significant statistically. Adrenal-enucleate controls displayed oliguria and Na+ retention, but normal K+ excretion and reduced Na+/K+. Nitrendipine did not modify oliguria or antinatriuresis or affect Na+/K+. Mononephrectomized rats behave similarly, but in these nitrendipine abolished oliguria and improved Na+ excretion. The most characteristic nitrendipine effect in all three cases was a reduction in urine osmolality. This was particularly evident in adrenal-enucleated and mononephrectomized rats, in which control urine displayed a relative hyperosmolarity as compared with normal control values.