The effects of a calcium channel agonist, BAY K-8644, on renin release and renal function were examined in perfused rat kidneys. BAY K-8644 increased renal vascular resistance and reduced glomerular filtration rate, sodium excretion and urine flow in a dose-dependent manner. These actions were prevented by the calcium channel blocker nifedipine. BAY K-8644 had no significant effect on basal renin secretion and failed to prevent renin stimulation by low-perfusion pressure or isoproterenol. The inhibitory effect of high-perfusion pressure on renin secretion was attenuated by the calcium entry blocker verapamil but not by nifedipine. Thus, if voltage-dependent calcium channels in the juxtaglomerular cell membrane participate in the regulation of renin release then these channels appear to be very insensitive to blockade or augmentation by 1,4-dihydropyridines.