PROLONGED IN-VITRO EXPOSURE OF BROILER ADIPOCYTES TO SOMATOSTATIN ENHANCES LIPOLYSIS AND INDUCES DESENSITIZATION OF ANTILIPOLYSIS

Adipocytes isolated from abdominal fat of female broilers and maintain ed in primary culture were used to characterize acute and chronic effe cts of somatostatin (SRIF) on lipolysis and antilipolysis and to deter mine whether desensitization and cross-regulation phenomena are involv ed in the regulation of adipocyte metabolism by SRIF and glucagon. Acu te exposure of adipocytes to SRIF resulted in a dose-dependent inhibit ion of basal and glucagon-stimulated lipolysis. The potency and extent of lipolysis inhibition by SRIF were inversely related to the dose of glucagon used to stimulate lipolysis. Preincubation of adipocytes wit h SRIF induced a dose-response and time-dependent increase in the set- point of lipolysis. Adipocyte sensitivity to glucagon was not altered by SRIF pretreatment. In contrast, preincubation with SRIF reduced adi pocyte sensitivity and maximal responsiveness to SRIF, The pattern and extent of antilipolysis attenuation were dependent on the dose and ti me of preincubation with SRIF as well as on the concentration of gluca gon used to acutely stimulate lipolysis. In two experiments, the atten uation of antilipolysis induced by SRIF pretreatment was observed in t he absence of enhanced lipolysis, whereas in one experiment enhanced l ipolysis was observed in the absence of attenuated antilipolysis. Thes e results indicated that persistent activation of antilipolysis by SRI F increased the set-point of lipolysis by sensitizing (i.e., cross-reg ulating) lipolysis and by desensitizing antilipolysis.