The renal hemodynamic response to pressor substances in the diseased kidney has been suggested to be different from that in the normal kidney. The aim of this study was to investigate the effects of endothelin and angiotensin II on renal hemodynamics in experimental nephritis induced by the administration of antithymocyte serum in Wistar rats. This model showed mesangiolytic lesions in the glomeruli on day 2 and hypercellular lesions on day 8. Prior to the injection of either endothelin or angiotensin II, the glomerular filtration rate and renal plasma flow were significantly lower in model rats on day 2 or day 8 than in the control rats. The basal glomerular filtration rate and renal plasma flow on day 8 were negatively correlated with the mesangium cell number. The injection of endothelin (0.5 ng/kg BW) led to a decrease in both renal plasma flow and glomerular filtration rate in rats on day 8 which was significantly greater than that in the control rats. Similarly, angiotensin II infusion (0.2 micrograms/kg BW) reduced both renal plasma flow and glomerular filtration rate in the rats on day 8 and the reductions were significantly greater than those in the control rats. In conclusion, renal hemodynamics in rats with mesangial proliferation of the kidney were more sensitive to both endothelin and angiotensin II than those in the normal kidney.