Fasting inhibits natriuretic peptides clearance receptor expression in rat adipose tissue

Objective and design: The early phase of weight loss indu ced by fasting is associated with diuresis, natriuresis and reduct ion in blood pressure through unclear mechanisms. Atri al natriuretic peptid e (ANP) is a cardiac hormone with potent natriuretic, diuretic and hypotensive effects mediated by ‘biologically active’ receptors (NPr-A). A second type of receptor mediates the clea rance of AN P (the clearance receptor, NPr-C). Since NPr-C appears to be abundant in adipose tissue, we analysed NPr-C and NPr-A gene expression in white and brown adipose tissue (WAT and BAT) as well as in renal cortex of fasting rats. Plasma ANP, cyclic GMP and aldosterone were also measured. Methods: Twelve male Wi star rats were deprived of food for about 50 h, and 12 other rats were fed ad libitum. Periepididymal WAT, interscapul ar BAT and left renal cortex were used for RNA extracti on and northern blot analysis w ith rat NPr-C and NPr-A complementary DNA probes labelled with ₃₂P-dCTP. Densitometric analysis of hybridi zation signals was corrected by β actin expression before statistical analysis. Blood was drawn for ANP, cyclic GMP (cGMP) and aldosterone radioimmunoassays, which were also measured in a group of six rats deprived of food for 25 h. Results: A dramatic decrease in NPr-C steady-state messenger RNA levels was observed both in WAT (about 3.6-fold, P