Modulation by sex hormones of the membranous transducing system regulating fatty acid mobilization in adipose tissue.

This review summarizes recent animal studies performed to determine the possible role played by sex hormones in the sex- and site-related differences characterizing adipocyte lipolytic activity. In both normal female rats and male hamsters, fat cells from deep intra-abdominal sites elicit higher catecholamine-stimulated lipolytic responses than subcutaneous adipocytes. By using ovariectomized rats, it was found that estradiol 'in vivo', while having no effect in subcutaneous cells, promotes catecholamine-stimulated lipolysis in deep intraabdominal adipocytes by increasing their adenylate cyclase catalytic activity. By using castrated hamsters, it was found that both deep intra-abdominal and subcutaneous fat cell lipolytic activities are equally sensitive to testosterone. In these cells, testosterone treatment promotes not only the beta-adrenergic lipolytic responses by increasing both the adenylate cyclase catalytic activity and the Gs alpha level, but also enhances the alpha 2-adrenergic antilipolytic responses through a transcriptional activation of the alpha 2-adrenoceptor expression. These experiments demonstrate that in some, but not all, white adipocytes the adrenergic signal transducing system regulating lipolysis is a target for sex hormones. This finding may have potential importance in the understanding of the mechanisms underlying the sex-related regional specificities of adipose tissue metabolism and distribution.