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 maintained in primary culture were used to characterize acute and chronic effects of somatostatin (SRIF) on lipolysis and antilipolysis and to determine whether desensitization and cross-regulation phenomena are involved in the regulation of adipocyte metabolism by SRIF and glucagon. Acute exposure of adipocytes to SRIF resulted in a dose-dependent inhibition 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 with 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 adipocyte sensitivity and maximal responsiveness to SRIF. The pattern and extent of antilipolysis attenuation were dependent on the dose and time of preincubation with SRIF as well as on the concentration of glucagon used to acutely stimulate lipolysis. In two experiments, the attenuation of antilipolysis induced by SRIF pretreatment was observed in the absence of enhanced lipolysis, whereas in one experiment enhanced lipolysis was observed in the absence of attenuated antilipolysis. These results indicated that persistent activation of antilipolysis by SRIF increased the set-point of lipolysis by sensitizing (i.e., cross-regulating) lipolysis and by desensitizing antilipolysis.