RESUMO
1. The objetve of the present study was to determine whether chronic salt load or depletion leads to adaptive changes in Kinetics of atrial natriuretic factor (ANF) binding and/or responsiveness to ANF. We measured the equilibrium binding and the stead-state dose response effects of ANF1-28 on isolated kidneys from rats kept on a high (H) or low (L) salt diet for 15 days. 2. Twenty-four sodium excretion was 5.90 ñ 0.46 mEq for H vs 0.06 ñ 0.01 mEq for L(P<0.01). Plasma levels of immunoreactive ANF for H (42.2 ñ 3.9pg/ml) were not significantly different from those for L (35.2 ñ 5.3 pg/ml). s. There were no significant differences in distribution, apparent density or affinity of ANF specific binding sites determined in non-filtering isolated kidneys from rats kept on the H or L salt diet. 4. Dose-response curvas for the hemodynamic and excretory effects of ANF1-28 in filterin isolated kidneys from rats kept on the H salt diet were not different from those of rats kept on the L salt diet. In contrast, the vasorelaxant response to ANF 1-28 in isolated kidneys preconstricted by adding serum from 24-h nephrectomized rats to the prefusate (generation of angiotensin II) was significantly more pronounced in kidneys from ratas chronically adapted to the high-salt diet. 5. This effect of ANF may contribute to the increased renal plasma flow and glomerular filtration rate occuring under conditions of chronic salt loading in intact animals