SITE-SPECIFIC EFFECTS OF SYMPATHECTOMY ON THE ADRENERGIC CONTROL OF LIPOLYSIS IN HAMSTER FAT-CELLS

Regional variations in the response of adipose tissue to lipolytic sti muli have been suggested to be involved in the development of visceral adiposity-related morbidity and mortality. Moreover, studies in human s and in laboratory rodents such as hamsters have shown that the respo nse of adipocytes to catecholamines depends on their anatomical origin . The aim of the present study was to investigate the relative involve ment of the adrenal medulla and of the sympathetic nervous system on r egional differences in the adrenergic control of lipolysis in isolated adipocytes from inguinal and epididymal adipose tissues. For this pur pose, we carried out adrenal demedullation or chemical sympathectomy i n hamsters. The results confirmed that epididymal adipocytes were sign ificantly more responsive to beta-adrenergic stimulation than inguinal adipocytes (p less than or equal to 0.05). This site specificity coul d originate at a step distal to receptors since tissues exhibited a si milar number of binding sites for [I-125]cyanopindolol. No significant regional differences were observed in the alpha(2)-adrenergic antilip olytic response, with the exception of the clonidine EC(50). A 14-day sympathectomy significantly increased the beta-adrenergic lipolytic re sponse only in inguinal adipocytes (p less than or equal to 0.05), and increased the alpha(2)-adrenergic response only in epididymal adipocy tes (p less than or equal to 0.05). On the other hand, adrenal demedul lation had no effect on both adrenergic pathways. These results sugges t that the sympathetic tone of adipose tissues could be involved in th e alpha(2)- and beta-adrenergic site-specific response in hamster fat cells. The 33% increase of the beta-response in inguinal fat cells and the 38% increase of the alpha(2)-response in epididymal fat cells als o suggest that the sympathetic pathway favors the lipolytic activation of the epididymal adipose tissue.