The effect of manganese on lipogenesis, lipolysis, adenosine 3',5' cyclic monophosphate and cyclic nucleotide phosphodiesterase activity in adipocytes from NZY mice

The insulin-like action of Mn2+ was investigated in adipocytes isolated from male mice of the NZY strain. In agreement with previous reports Mn2+ was found to stimulate both the oxidation of U-14C]glucose to CO2 and the incorporation of U-14C]glucose into total lipid and fatty acid, and to inhibit lipolysis stimulated by epinephrine, cyclic AMP or theophylline. The maximum effect of Mn2+ was greater than that of a maximal concentration of insulin and when both agents were present in these concentrations the effect was similar to that observed with Mn2+ alone. Mn2+ lowered the level of cyclic AMP in adipocytes incubated with isoproterenol. The effect was seen as early as 1 minute and it was greater than a maximal concentration of insulin. When Mn2+ was added to suspensions of adipocytes it increased the activity of the membrane-bound low Km cyclic nucleotide phosphodiesterase in subsequently prepared homogenates. The enzyme was stimulated 1.8-fold by Mn2+ compared with a 1.7-fold stimulation by insulin and a 2-fold stimulation in the presence of both Mn2+ and insulin.