Effects of atrial natriuretic factor on glucose metabolism in isolated adipocytes

To investigate the role of natriuretic peptide receptors (NPRs) on adipocytes, the effect of atrial natriuretic factor (ANP) on the incorporation of glucose into lipids and CO2 production was studied. Rat adipocytes from the white fat surrounding the mesenteric artery were used. ANP (10(-6) M) significantly increased basal CO2 production (1.36 fold), but had no effect in the presence of insulin. ANP did not modify lipid incorporation. Incubations were carried out with < 4 x 10(5) cells ml-1 as the effects of ANP diminished with higher concentrations. The increase generated by ANP was dose dependent (EC50, 4 x 10(-9) M), and was not reproduced by des [Gln18, Ser19, Gly20, Leu21, Gly22) ANP(4-23) NH2 (c-ANP, 10(-7) M), C-type natriuretic peptide (CNP, 10(-7) M) or 8-bromo-cGMP (10(-3) M). However, co-incubation of c-ANP (10(-7) M) and CNP (10(-7) M) increased CO2 production. In the presence of isoproterenol (10(-6) M), ANP had no effect. Incubation with isobutylmethylxanthine (0.5 x 10(-3) M) significantly decreased basal CO2 production (to 30%), and this was not altered by ANP co-incubation. Thus, ANP appears to act via NPR-A to modulate oxidative glucose metabolism, but not through alteration of cGMP or cAMP production.