EFFECTS OF RENAL VENOUS PRESSURE ELEVATION ON RENAL HEMODYNAMICS, URINE FORMATION AND RENIN RELEASE

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Effects of renal venous pressure (RVP) elevation on the renal hemodynamics, urine formation and renin secretion rate (RSR) were studied in the pentobar-bital anesthetized dogs. Gradual increment of RVP produced no changes in RBF and GFR till 30 mmHg but a significant decrease in them at RVP above 35 mmHg. The urine flow response to RVP elevation was divided into two groups: an increased urine flow with an increase of sodium excretion and a decreased urine flow with a decrease of sodium excretion. In the former group, gradual RVP elevation produced a significant increase in U_NaV, Na/K ratio and T^C_H20 without changes in U_KV and C_osm, while the latter group showed a decrease in U_NaV, U_KV and T^C_H20. Renin secretion rate (RSR), the product of RPF and renal venous-arterial difference of plasma renin activity, increased significantly as function of RVP elevation. This RSR increment seemed to be independent of changes in RBF, GFR, urine flow, or U_NaV and the increased mechanism of RSR was discussed. It is concluded that tubular handling of sodium is not essential but intrarenal baroreceptor mechanism seems to be responsible for renin release in case of RVP elevation.