DISSOCIATION BETWEEN FILTERED LOAD OF SODIUM AND ITS RATE OF EXCRETION IN THE URINE*

Abstract

The relationship between filtered load of Na and the rate of urinary Na excretion (UNaV) when plasma Na concentration was increasing and filtered load decreasing as a consequence of the infusion of a solution of hypertonic saline and the simultaneous disproportionate depression of glomerular filtration rate was examined in anesthetized dogs. No direct relationship between filtered load of Na and UNaV was found. UnaV was markedly elevated over control values despite a decreased filtered load. Several explanations for the findings are presented. It is concluded that factors other than filtered load influence UNaV, and the data imply that plasma Na concentration may be one of the regulating influences.