Intrarenal distribution of blood flow and renin release during renal venous pressure elevation

Abstract

The effects of renal venous pressure (RVP) elevation on the intrarenal distribution of blood flow and renin secretion were studied in mongrel dogs anesthetized with pentobarbital sodium. The intrarenal distribution of blood flow was determined with the radioactive xenon (133Xe) washout technique. Elevation of RVP to 30 mm Hg caused a significant change in the intrarenal distribution of blood flow and a significant increase in renin secretion rate without changes in total renal blood flow (RBF) and glomerular filtration rate (GFR). At this RVP, the percentage of distribution and relative volume increased significantly in the second flow component and decreased significantly in the first flow component. When RVP was elevated above 30 mm Hg, further redistribution of flow from first flow component to second flow component occurred and RBF and GFR began to decrease. Thus, there was an inverse relationship between RVP and the percentage of RBF into first flow component (P<0.001) and a direct relationship between RVP and the fraction of blood flow into second flow component (P<0.001). The percentage of the third flow component correlated linearly with RVP elevation (P<0.01). Renin secretion rate (RSR), the product of renal venous arterial difference of plasma renin activity and renal plasma flow, was increased significantly by RVP elevation between 20 and 50 mm Hg. Accordingly, RSR was inversely correlated with the change in the fraction of blood flow and relative volume of first flow component (P<0.01). These findings suggest that changes in intrarenal hemodynamics might be a trigger for renin secretion.