Insulin-sensitive adenosine 3′,5′-cyclic monophosphate phosphodiesterase of hepatocyte plasma membrane

Adenosine 3′-,5′-cyclic monophosphate phosphodiesterase (EC 3.1.4.17) has been investigated in rat liver as to its insulin sensitivity. Hormone action has been assayed in vitro on a liver hemogenate purified by DEAE-cellulose column chromatography, on isolated hepatocytes, on isolaetd plasma membranes. The DEAE-cellulose chromatography purified homogenate showed no sensitivity to insulin, whereas isolated hepatocytes incubated in presence of insulin showed increased phosphodiesterase activity in a plasma membrane-containing fraction. The plasma membrane-bound enzyme, which shows both high and low affinity components, was significantly stimulated after hormonal treatment; this effect being dependent on a V increase of the low K_m form.