The Effect of Manganese on Lipogenesis, Lipolysis, Adenosine 3′,5′ Cyclic Monophosphate and Cyclic Nucleotide Phosphodiesterase Activity in Adipocytes from NZY Mice

Summary The insulin-like action of Mn 2+ was investigated in adipocytes isolated from male mice of the NZY strain. In agreement with previous reports Mn 2+ was found to stimulate both the oxidation of [U- 14 C]glucose to CO 2 and the incorporation of [U- 14 C]glucose into total lipid and fatty acid, and to inhibit lipolysis stimulated by epinephrine, cyclic AMP or theophylline. The maximum effect of Mn 2+ 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 Mn 2+ alone. Mn 2+ 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 Mn 2+ 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 Mn 2+ compared with a 1.7-fold stimulation by insulin and a 2-fold stimulation in the presence of both Mn 2+ and insulin.