Effects of castration, dietary fat and adipose tissue sites on adipocyte plasma-membranes cyclic amp phosphodiesterase activity in the pig

1. 1. cAMP Phosphodiesterase activity and kinetic parameters ( K m , and V max ) were measured in subcutaneous and perirenal adipocyte plasma membranes from Large White male and castrated pigs. The animals were fed a control low fat diet or a sunflower diet enriched with linoleic acid (C18:2 n −6). 2. 2. Phosphodiesterase activity, low K m and V max were lowered by castration. 3. 3. In animals fed the sunflower diet, Phosphodiesterase activity decreased without affecting either K m or V max . 4. 4. Phosphodiesterase activity was higher in perirenal sites than in subcutaneous ones, particularly in male pigs. This may be explained by a lower K m or a higher cAMP phosphodiesterase affinity to cAMP in perirenal sites. 5. 5. Theophylline was a potent inhibitor of phosphodiesterase activity principally in perirenal sites. 6. 6. The intermediate role of cAMP phosphodiesterase in adenylate cyclase activity and lipolytic processes is discussed.