Effects of the beta-adrenoceptor blocker nipradilol on renal microcirculation in a rat model: A comparative study with propranolol

Abstract

The objective of the present study was to compare the effects of the vasodilating nonselective beta-adrenoceptor blocker nipradilol on renal microvasculature with those occurring with propranolol, a typical nonselective beta-adrenoceptor blocker. Hydronephrosis was induced by ligation of the left ureter in seventeen 8-week-old stroke-prone, spontaneously hypertensive rats. The experiment was performed 2 months after the surgery. The hydronephrotic kidney was split longitudinally and spread out as a thin sheet, and the renal microvasculature was observed directly under a light microscope. Intravenous administration of nipradilol 200 μg/kg as a bolus caused a significant decrease in the systolic blood pressure (−36 mm Hg) at 5 minutes. The afferent arteriole was significantly dilated transiently (+13% in diameter) at 10 minutes. The changes in the efferent arteriole were not statistically significant. The glomerular blood flow was statistically significantly increased (+22%) at 10 minutes. Intravenous administration of propranolol 600 μg/kg did not cause statistically significant changes in the systolic 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 flow despite a significant decrease in the systolic blood pressure. This vasodilating effect on the afferent arteriole was not observed with propranolol.