ENHANCED LIPOLYSIS FROM BROILER ADIPOCYTES PRETREATED WITH PANCREATIC-POLYPEPTIDE

Broiler adipocytes in culture were used to determine whether prolonged preincubation with an antilipolytic hormone, pancreatic polypeptide, enhances lipolysis by inducing desensitization of lipolysis inhibition . Preincubation of broiler adipocytes with pancreatic polypeptide resu lted in a dose-response and time-dependent enhancement (P < .05) of ba sal and glucagon-stimulated lipolysis. Lipolysis was enhanced at 4 and 24 h but not at .5 h of pretreatment. Acute inhibition of basal lipol ysis was unaffected by long-term (24 h) exposure of adipocytes to a ma ximally effective dose (12 nM) of pancreatic polypeptide. Thus, desens itization of lipolysis inhibition cannot explain the enhanced lipolysi s from pancreatic polypeptide-treated adipocytes. However, preincubati on with 12 nM pancreatic polypeptide for 24 h reduced (P < .05) pancre atic polypeptide and somatostatin inhibition of lipolysis stimulated b y glucagon. Moreover, basal lipolysis and submaximal lipolysis were en hanced to a similar extent (27 vs 29 nmol/h) but to a greater (P < .05 ) extent (27 vs 13 nmol/h) than maximal lipolysis when adipocytes were exposed to 12 nM pancreatic polypeptide for 24 h. These results sugge st that the enhanced lipolysis induced by prolonged exposure of adipoc ytes to pancreatic polypeptide resulted from increased activity of hor mone-sensitive lipase and activators of this enzyme and not from atten uation of lipolysis inhibition.