Comparison of the natriuresis and chloruresis associated with glomerular hyperfiltration induced by atrial...

The impact on renal sodium chloride reabsorption of an acute increase in glomerular filtration rate (GFR) induced by atrial natriuretic factor (ANF) or glucagon was examined in the conscious rat. These hormones have no direct effect on proximal solute transport and have opposite effects on distal transport. ANF and glucagon increased GFR to a comparable extent (2.0 +/- 0.2 to 3.5 +/- 0.4 ml/min, p less than 0.01, and 1.9 +/- 0.1 to 3.3 +/- 0.1 ml/min, p less than 0.001, respectively). While most (95-97%) of the increment in filtered sodium chloride was reabsorbed, a small portion (3-5%) escaped tubular reabsorption. Absolute sodium and chloride urinary excretion rates increased similarly in response to each hormone, by two- to three-fold. Slightly imperfect load-dependent sodium chloride reabsorptive response by the nephron, despite opposite direct effects on distal nephron transport, may account for the observed natriuresis and chloruresis associated with the acute glomerular hyperfiltration induced by ANF or glucagon administration.