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

Blood pressure (BP) is rapidly normalized when removing the obstruction fro m the renal artery of a two-kidney, one-clip renovascular hypertensive rat (unclipping). This study tested whether efferent renal nerve stimulation (E RNS) of the unclipped kidney affects this drop in BP or the associated chan ges in diuresis-natriuresis and regional renal blood flow. Three groups of anesthetized renovascular hypertensive Wistar rats were studied: 1) W-C (ti me control); 2) W-UC (unclipped after 30 min); and 3) WUC+NS (unclipped aft er 30 min, with ERNS at 5 Hz for 2 h). Renal excretion and regional hemodyn amics (laser Doppler) were monitored in the unclipped kidney. Medullary and cortical blood perfusion increased by 84% and 95%, respectively, in W-UC 3 0 min after unclipping (P < .001) but only with 8% and 9%, respectively, in WUC+NS (P = NS). Unclipping induced a marked increase in diuresis-natriure sis that was largely unaffected by ERNS. In W-UC and WUC+NS BP returned to normotensive levels within 4 h. However, during the first 30 min, average B P decreased significantly less in WUC+NS (9%, 20 mm Hg) than in W-UC (16%, 35 mm Hg) (P < .05). ERNS at 5 Hz effectively prevented the increase in med ullary 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 hypertensi ve rat occurs largely independently of: ERNS and an increase in medullary b lood perfusion. (C) 1999 American Journal of Hypertension; Ltd.