Differences in beta-adrenergic receptor densities in omental and subcutaneous adipose tissue from obese African American and Caucasian women.

African American women lose less weight and at a slower rate than Caucasian women under the same weight loss conditions. This is likely due to decreased mobilization of fat, possibly involving differences in the responsiveness of adipose tissue to adrenergic stimulation. To better understand the causes behind the decreased lipolysis in African American women, this study was initiated to determine if there were differences in the numbers and affinities of beta adrenoreceptors in omental and subcutaneous adipose tissue of obese African American and Caucasian women. We determined the number of beta receptors using a nonselective antagonist and found the total number of receptors in both omental and subcutaneous adipose tissue preparations were higher in African American than Caucasian women. beta(1)(,) beta(2), and beta(3) densities were higher in omental adipose tissue (P <.05), but not different in the subcutaneous tissue of the African American women. No racial differences in kd values for adrenergic agents (agonists and antagonists) were found with regard to beta(1), beta(2), or beta(3) receptors in either the omental or the subcutaneous preparations. beta(1) and beta(2) receptor protein (mass) was significantly increased in African American omental tissue preparations, but not subcutaneous. Our in vitro data demonstrating increased beta receptor numbers in omental tissue from obese African Americans suggest that the potential for lipolysis would be higher in these women. Future studies should determine the biologic significance of the differences in the beta adrenergic receptors in vivo.