1. This study investigates the effect of nifedipine on cyclosporin A nephrotoxicity in the spontaneously hypertensive rat.
2. Cyclosporin A, administered daily by subcutaneous injection at 25 mg/kg body weight for 14 days, induced a significant reduction in glomerular filtration rate (35.3%) and effective renal plasma flow (45.0%), and an increase in renal vascular resistance (219%). Using this regimen, tubular, glomerular or vascular morphological damage was not evident on light microscopy.
3. The administration of nifedipine simultaneously with cyclosporin A from day 1 prevented the characteristic decline in renal function and increase in renal vascular resistance. However, the administration of nifedipine to spontaneously hypertensive rats previously exposed to cyclosporin A for 7 days failed to improve renal haemodynamics.
4. This study suggests that the beneficial effect conferred by nifedipine on cyclosporin A nephrotoxicity is present only when treatment is initiated simultaneously with cyclosporin A.