Renal response to measured blood volume expansion in differently hydrated dogs

¹ Department of Physiology, University of Alberta, Edmonton, Canada

Infusion of artificial blood in anesthetized dogs produced expansion of intravascular and extravascular volumes, uncomplicated by changes in osmotic pressure or evidence of histamine release. The resulting diuresis and natriuresis was not accounted for by observed effects of exchange of circulating blood for infusate. The stimulus to the renal response after infusion must then have included the parameter of extracellular volume. The diuresis could not be explained as the result of measured alterations in renal hemodynamics, but the findings do not allow distinction between hormonal or other influences on tubular function. In animals prehydrated with saline, the diuretic and natriuretic responses to infusion were significantly greater than in normally hydrated dogs, whereas in dehydrated dogs the responses were significantly smaller. In these three groups the infusions produced comparable initial measured increases in intravascular volume. It is proposed that the renal regulation of extracellular fluid volume in the dog is determined by graded potentiation by the existing extravascular volume of the response to intravascular expansion.