Effect of orchiectomy on renal function in control and diabetic rats with chronic inhibition of nitric oxide

1. Male gender is associated with higher blood pressure (BP) and more rapid loss of renal function in a spectrum of clinical and experimental renal diseases, including diabetic nephropathy. Consequently, modulation of testosterone levels could exert beneficial effects in the diabetic kidney. 2. The aim of the present study was to determine whether testosterone deficiency (orchiectomy) could influence BP and renal function in streptozotocin-diabetic rats, with or without accelerated endothelial dysfunction achieved by chronic inhibition of nitric oxide (NO) synthesis using N(G)-nitro-L-arginine methyl ester (l-NAME; 40-100 mg/L in the drinking water for 2 weeks), as well as in age-matched non-diabetic rats subjected to the same interventions. 3. Orchiectomy did not affect L-NAME-induced increases in BP in non-diabetic or diabetic rats. In non-diabetic rats, orchiectomy prevented L-NAME-induced increases in proteinuria. These effects on proteinuria were not observed in diabetic rats. In non-diabetic rats, orchiectomy had no effect on renal haemodynamics in animals receiving vehicle and did not affect L-NAME-induced changes in renal haemodynamics, characterized by reductions in renal plasma flow (RPF) and higher filtration fractions (FF). In intact diabetic rats, L-NAME treatment resulted in lower RPF. This difference was not observed in diabetic rats subjected to orchiectomy, although L-NAME-treated diabetic orchiectomized rats had lower RPF and higher FF compared with vehicle-treated intact diabetic rats. 4. In conclusion, we report modest beneficial effects of orchiectomy on proteinuria in normal, but not in diabetic, rats with inhibition of NO production. This suggests that testosterone reduction does not attenuate the deleterious impact of the diabetic metabolic milieu in the kidney.