Increased alpha 2- but similar beta-adrenergic receptor activities in subcutaneous gluteal adipocytes from females compared with males.

alpha 2 and beta-adrenergic binding and action were studied in subcutaneous adipocytes from the gluteal region in females and males. The beta-selective antagonist [3H]dihydroalprenolol and the alpha 2-selective antagonist [3H]yohimbine were used to identify the beta- and the alpha 2-receptor, respectively. The biological effects mediated by these receptors were determined by measuring the glycerol release induced by isoproterenol (beta-receptor agonist) and by clonidine (alpha 2-receptor agonist). The study consisted of health volunteers (eighteen females and fifteen males). Compared to men the alpha 2-receptor binding was increased by 73% (P less than 0.01) in adipocytes from females. From Scatchard analysis it was determined that the increased binding was due to an increased receptor number (438 v. 262 fmol mg-1 protein, P less than 0.001) with unaltered Kd (1.18 v. 1.35 nmol l-1, P greater than 0.05). This increased alpha 2-receptor binding in female and adipocytes was associated with a significantly increased sensitivity (P less than 0.05) and maximal antilipolytic effect of clonidine (P less than 0.05). The beta-receptor binding was similar in adipocytes from females and males. However, isoproterenol was significantly more lipolytic in female adipocytes (P less than 0.01). Since the combination of theophylline and adenosine deaminase also was significantly more lipolytic in female adipocytes the enhanced effect of isoproterenol then seemed to be due to mechanisms not directly related to the hormone-beta-receptor binding. Finally, the mixed beta- and alpha 2-receptor agonist, adrenaline showed biphasic effects on lipolysis, with stimulatory effect at low concentrations (less than 500 nmol l-1) and pronounced inhibitory effect at higher concentrations (greater than 1 mumol l-1).(ABSTRACT TRUNCATED AT 250 WORDS)