The control of sodium excretion following saline infusion in dogs.

Abstract

The increase in fractional excretion of sodium following intravenous infusion of saline has been investigated in dogs fed with sodium-rich or poor diets after transplantation to the neck of these animals of kidneys removed from dogs submitted previously to either diet. The response of “in situ” and of transplanted organs has been compared in the four possible combinations of perfusors and kidney donors. No significant differences were observed between the four series, for the same net saline load, in arterial and venous pressures, extravascular and intravascular expansion, or blood dilution. The response in each series was independent of extracellular expansion and was best related to the degree of blood dilution. However, the magnitude of the response to the same net saline load depended on a resetting of the sensitivity of the kidney itself to the blood changes, this resetting depending on the previous dietary sodium balance. This sensitivity was related also to the presence in the blood of a potentiating material which might be, at least partly, of renal origin, and which might represent an intrarenal mediator of the natriuretic response.