Lipase activity in the fat cake and aqueous phase of adipose tissue homogenate of fed, fasted and fasted-refed rats.

Abstract

Abstract. 1. Free fatty acid production by the fat cake of adipose tissue was found to be much greater in fasted‐refed than in fasted and fed rats, respectively. Preincubation with adrenalin and dibutyryl cyclic AMP stimulated lipase activities in fasted and fed rats, but not in fasted‐refed rats. Basal lipase activity in the fat cake of fasted‐refed rats was higher than adrenalin or dibutyryl cyclic AMP activated lipase activity of fasted or fed rats. Activation of lipase activity by refeeding lasted for several days.—2. Lipase activity in the aqueous phase of adipose tissue homogenate of all rats was in the same range.—3. Free fatty acid release during the assay of lipase in the fat cake proceeded for a period of up to 120 minutes although not in an entirely linear manner. The ratio of free fatty acids to glycerol release was 2.9. The pH optimum of the reaction was 7.4. NaCl, NaF, protamine and heparin markedly inhibited the lipase reaction. Heparin in the preincubation medium did not reduce the lipase activity in the fat cake.— 4. The very active triglyceride lipase activity of adipose tissue of fasted‐refed rats explains earlier findings showing that intact adipose tissue of fasted‐refed rats exhibits a very high glycerol release. It appears that tissue levels of triglyceride lipase increase during refeeding under the influence of insulin, i.e. at a time when the level of cyclic AMP in the tissue supposedly is low.