Studies on the Regulation of Phosphodiesterase in Human Adipose Tissue in Vitro

Abstract

The influence of several agents known to affect the rate of lipolysis or the phosphodiesterase (PDE) activity inrat adipose tissue was studied in human adipose tissue in vitro. Only insulin, catecholamines, prostaglandin E₁,and _cAMP increasedPDE activity in man (by 20-40% over the controlvalues). In dose-response studies, it was found that the ED₅₀values for insulin and isopropyl noradrenaline were of the samemagnitude as the previously observed ED₅₀values fo lipolysisin human adipose tissue. The time course for insulin and isopropylnoradrenalineshowed maximum stimulation after 10 min,followed by a decline, with the curve approaching zero at 60min. I subcellular fractions of adipose tissue, the highest specificPDE activity was found in the particulate fraction, in whichthe effects of both insulin and isopropyl noradrenalineweremost marked. It is concluded that the stimulatory effect ofcatecholamines on PDE maybe one reason for the failure ofthese agents to produce a sustained increase in the _cAMPleveland that the effect of insulin on PDE may be one mechanismby which insulin reduces the rate of lipolysis. (J Clin EndocrinolMetab56: 501, 1983)