Similar atypical beta-adrenergic receptors mediate in vitro rat adipocyte lipolysis and colonic motility inhibition.

We investigated the putative common nature of the rat atypical beta-adrenoceptors mediating white adipocyte lipolysis and proximal colon motility inhibition, using the non-selective antagonist alprenolol and agonist isoprenaline and the selective agonists SR 58611A and BRL 37344. Results in either isolated intestinal and fat tissues were consistent with: isoprenaline acting through both typical (beta 1, beta 2) and typical beta-adrenoceptors; SR 58611A and BRL 37344 acting solely through the latter. The identical pA2 values obtained with alprenolol, irrespective of the tissue and the selective agonist (SR 58611A or BRL 37344) used, support the high functional homology of the atypical beta-adrenoceptors in rat colon and adipocytes.