EFFECTS OF THE BETA-ADRENOCEPTOR BLOCKER NIPRADILOL ON RENAL MICROCIRCULATION IN A RAT MODEL - A COMPARATIVE-STUDY WITH PROPRANOLOL

The objective of the present study mas to compare the effects of the v asodilating nonselective beta-adrenoceptor blocker nipradilol on renal microvasculature with those occurring with propranolol, a typical non selective beta-adrenoceptor blocker. Hydronephrosis was induced by Lig ation of the left ureter in seventeen 8-week-old stroke-prone, spontan eously hypertensive rats. The experiment mas performed 2 months after the surgery. The hydronephrotic kidney was split longitudinally and sp read out as a thin sheet, and the renal microvasculature was observed directly under a light microscope. Intravenous administration of nipra dilol 200 mu g/kg as a bolus caused a significant decrease in the syst olic blood pressure (-36 mm Hg) at 5 minutes. The afferent arteriole w as significantly dilated transiently (+13% in diameter) at 10 minutes. The changes in the efferent arteriole mere not statistically signific ant. The glomerular blood flow was statistically significantly increas ed (+22%) at 10 minutes. Intravenous administration of propranolol 600 mu g/kg did not cause statistically significant changes in the systol ic blood pressure, the afferent arteriolar diameter, or the glomerular blood flow. The efferent arteriole showed a statistically significant constriction (-16% in diameter) at 20 minutes. In summary, nipradilol dilated the afferent arteriole and increased the glomerular blood flo w despite a significant decrease in the systolic blood pressure. This vasodilating effect on the afferent arteriole was not observed with pr opranolol.