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The expression of beta-adrenoceptors (BAR) was investigated in abdominal and gluteal fat cells of 32 nonobese men and women using radioligand binding and RNA excess solution hybridization. In both sexes the number of BAR binding sites was about twice as high in abdominal as in gluteal fat cells (P less than 0.01). Northern blot analysis of total RNA from adipose tissue showed hybridization of the BAR1 probe to an mRNA species of about 2.5 kb and of the BAR2 probe to an mRNA species of approximately 2.2 kb. The steady-state mRNA levels of BAR 1 and BAR 2 were also about twice as high in abdominal as in gluteal adipocytes of men and women (P less than 0.01). In abdominal fat cells the mRNA levels were approximately 45 and 30 molecules/cell for BAR1 and BAR2, respectively. There were no regional or sex variations in BAR 1 and BAR 2 mRNA stability. The apparent half-life of mRNA for both receptor subtypes was approximately 6 h in both regions. The mRNA levels for beta actin did not differ between the two regions in either sex. Thus, differences in expression of the genes encoding for BAR 1 and BAR 2 can explain why abdominal fat cells have more BAR than gluteal fat cells. This variation in gene expression may be a molecular mechanism underlying the well known regional differences in catecholamine-induced lipolysis activity between central and peripheral adipose tissue.
Arner et al. (Thu,) studied this question.