This study examined the influence of a calcium channel antagonist, nitrendipine, on blood pressure and kidney function in a rat model of chronic renal failure. Additionally, the effects of low frequency renal nerve stimulation were studied in the presence and absence of nitrendipine. Male Wistar rats were fed a diet high in adenine for 4 weeks and then acutely anaesthetised and prepared for renal functional measurements. Blood pressure was elevated but renal blood flow and glomerular filtration rate were reduced, between 30 to 50%, urine flow and absolute sodium excretion were lower and fractional sodium excretion was two to three times higher than in normal rats. Nitrendipine (0.25 microg/kg/min i.v.) decreased blood pressure at 114+/-7 mm Hg, by 11% (P<0.05), increased left renal blood flow, at 1.3+/-0.2 ml/min(-1) g(-1), by 16% (P<0.01), and urine flow, absolute and fractional sodium excretions, by between 50-83% (all P<0.05). Renal nerves stimulation (0.7-1.3 Hz, 15V, 0.2 ms) decreased (P<0.02) left renal blood flow by 10% but had no effect on excretory variables, irrespective of nitrendipine administration. These results show that in renal failure rats the vascular and tubular responses to nitrendipine are preserved. However, the neural regulation of tubular reabsorption is abolished in this experimental model, irrespective of nitrendipine administration.