No abstract

Systemic and renal hemodynamics, and plasma antinatriferic activity (AA) were measured before, during 2 h of saline loading, and for 1 h immediately after stopping saline infusion in dogs. During loading, mean arterial pressure (MAP), central venous pressure (CVP), renal blood flow (RBF), glomerular filtration rate (GFR), and AA increased as sodium excretion as (U_NaV) rose progressively. During the post-loading period, MAP, CVP, and AA returned to baseline, RBF and GFR remained elevated, while U_NaV fell. Only 52 ± 3% of the total sodium load was excreted during the study. These data show that AA is not regulated by the absolute volume of extracellular fluid. The correlation of AA with changes in systemic hemodynamics suggests ‘volume receptors’ in the resistance and/or capacitance circulation. The data suggest that the post-loading fall in U_NaV i_s due at least in part to decreased levels of a humoral natriuretic factor.