Effect of Change in Renal Venous Pressure Upon Renal Vascular Resistance, Urine and Lymph Flow Rates

Abstract

The usual increase in intrarenal resistance as a function of flow rate was augmented by elevation of venous pressure. The augmentation was more apparent in innervated than denervated kidneys. With blood flow rate held constant, resistance increased as a function of venous pressure in innervated kidneys but decreased slightly in denervated kidneys. The latter response was not different during administration of phentolamine, phentolamine and eserine or during perfusion of live innervated and dead kidneys with dextran. Resistance changes induced by elevation of only arterial pressure were the same in innervated and denervated kidneys. For a given arterial pressure in dead kidneys perfused with dextran, resistance was higher with venous pressure elevated than it was with pressure normal. Lymph flow rate increased as a function of venous pressure. Urine flow rate decreased as a function of venous pressure with blood flow rate uncontrolled but did not change when flow rate was held constant. Therefore, high renal vein pressures increase resistance by reflex active vasoconstriction as well as by passive vasoconstriction. The reduction in urine flow rate is in part related to these resistance controlling mechanisms.