Effects on regional renal blood flow when unclipping a two-kidney, one-clip hypertensive Wistar rat during renal nerve stimulation

Abstract

Blood pressure (BP) is rapidly normalized when removing the obstruction from the renal artery of a two-kidney, one-clip renovascular hypertensive rat (unclipping). This study tested whether efferent renal nerve stimulation (ERNS) of the unclipped kidney affects this drop in BP or the associated changes in diuresis-natriuresis and regional renal blood flow. Three groups of anesthetized renovascular hypertensive Wistar rats were studied: 1) W C (time control); 2) W UC (unclipped after 30 min); and 3) W UC +NS (unclipped after 30 min, with ERNS at 5 Hz for 2 h). Renal excretion and regional hemodynamics (laser Doppler) were monitored in the unclipped kidney. Medullary and cortical blood perfusion increased by 84% and 95%, respectively, in W UC 30 min after unclipping ( P < .001) but only with 8% and 9%, respectively, in W UC +NS ( P = NS). Unclipping induced a marked increase in diuresis-natriuresis that was largely unaffected by ERNS. In W UC and W UC +NS BP returned to normotensive levels within 4 h. However, during the first 30 min, average BP decreased significantly less in W UC +NS (9%, 20 mm Hg) than in W UC (16%, 35 mm Hg) ( P < .05). ERNS at 5 Hz effectively prevented the increase in medullary blood perfusion but did not affect the fall in blood pressure or the pressure diuretic/natriuretic response seen after unclipping. The results suggest that both the reduction in BP and the pressure-induced increase in diuresis/natriuresis seen when unclipping the 2K,1C renovascular hypertensive rat occurs largely independently of ERNS and an increase in medullary blood perfusion.