THE ROLE OF INTRARENAL PROSTAGLANDINS AND ANGIOTENSIN-II IN ACUTE CYCLOSPORINE-INDUCED VASOCONSTRICTION

Cyclosporine causes intrarenal vasoconstriction, which may account for its nephrotoxic effects. In this study we investigated the role of endogenous prostaglandins and angiotensin II in cyclosporine-induced intrarenal vasoconstriction. Split hydronephrotic kidneys in decerebrate rats (n = 16) were suspended in an environmentally controlled tissue bath. Interlobular, afferent, and efferent arteriolar diameters and red blood cell velocity were measured by in vivo video-microscopy and Doppler velocimetry. After topical application of cycloporine to the kidney in the tissue bath, a 12% +/- 2% constriction of the interlobular and a 28% +/- 5% reduction in interlobular blood flow occurred. The afferent and efferent arterioles also constricted by 13% +/- 2% and 10% +/- 3%, respectively. Prostaglandin inhibition with mefenemate augmented this vasoconstriction (16% +/- 2% at interlobular and 21% +/- 4% at afferent arterioles) and reduction in interlobular blood flow (38% +/- 8%) below baseline values. Mefenemate alone resulted in a 35% +/- 5% reduction in interlobular blood flow, which was not further augmented by cyclosporine. In contrast, local competitive angiotensin II-receptor inhibition with saralasin maintained blood flow after cyclosporine and prevented intrarenal vasoconstriction by cyclosporine. This suggests that prostaglandins protect against intrarenal vasoconstriction and that acute cyclosporine-induced vasoconstriction is mediated through angiotensin II receptors.