Effects of N-aralkyl substitution of beta-agonists on alpha- and beta-adrenoceptor subtypes: pharmacological studies and binding assays.
The pharmacological and binding properties of four beta-adrenomimetic drugs with N-alkyl substitutions (isoprenaline, terbutaline, salbutamol and soterenol) were compared with those of four corresponding drugs with N-aralkyl substitutions (protokylol, ME 506, salmefamol and zinterol). BD-40 A, a very powerful beta 2-agonist with a related chemical structure, was also included in this study. The beta 1- and beta 2-activities of these drugs were determined on guinea-pig atria and trachea, their alpha-adrenolytic activity was measured on rat aorta and their affinities (Ki) for alpha 1- and alpha 2-adrenoceptors on rat cortical membranes were assessed using [3H]prazosin and [3H]yohimbine. In this group of beta-agonists, substitution of the N-alkyl by an N-aralkyl group had a variable effect on the beta 2-selectivity whereas alpha-adrenolytic properties were always enhanced. An increase of the affinities (Ki) for both alpha 1- and alpha 2-adrenoceptors was found but the effect was much more pronounced for alpha 1-adrenoceptors. These results indicated that the alpha-adrenolytic activity observed with the N-aralkyl beta-agonists was selective for alpha 1-adrenoceptors.
D000318:Adrenergic beta-Agonists / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D008297:Male; D008566:Membranes / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013329:Structure-Activity Relationship; D015016:Yohimbine / Q000378:metabolism
D000318:Adrenergic beta-Agonists; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D015016:Yohimbine; D011224:Prazosin