Stereochemical aspects of beta-adrenoceptor antagonist-receptor interaction in adipocytes. Differentiation of beta-adrenoceptors in human and rat adipocytes.

In order to define further the possibilities and limitations of the use of rat adipocytes as a model for the study of β-adrenoceptor antagonism in human adipose tissue, the potencies against isoprenaline induced lipolysis of the stereoisomers of propranolol, alprenolol, nifenalol and practolol on human and rat adipocytes were determined. All four compounds showed higher stereoselectivity on human than on rat adipocyte β-adrenoceptors, the dextrorotatory isomers being approximately equipotent in both species, in contrast to the levorotatory isomers which were considerably more potent on human adipocyte β-adrenoceptors. It is suggested that human and rat adipocyte β-adrenoceptors are very similar, except for the site that interacts with the β-hydroxy-group which is present in the sidechain of most β-adrenoceptor stimulating and blocking agents.