Studies on the receptor profile of bisoprolol

The in vitro binding affinity of (+/-)-1-[4-(2-isopropoxyethoxymethyl)-phenoxy]-3-isopropylamino-2- propranol hemifumarate (bisoprolol, EMD 33 512) to beta 1-, beta 2-, alpha 1-, alpha 2-, D1-, D2-, 5-HT2- and muscarinic cholinergic receptors of rat was compared with that of atenolol, betaxolol and propranolol. Bisoprolol showed a high specific binding affinity to beta 1-adrenoceptors (heart) and a low specific binding affinity to beta 2-adrenoceptors (lung). The beta 1-selectivity of bisoprolol (beta 2/beta 1 = 34.7) proved to be higher than that of atenolol (8.7) and betaxolol (12.5). Propranolol (0.59) was non-selective as expected. Bisoprolol and atenolol exhibited no remarkable binding affinity to alpha 1-, alpha 2-, D1-, D2-, 5-HT2- and muscarinic cholinergic receptors at concentrations up to 1 X 10(-4) mol/l. For betaxolol binding affinities for alpha 2-, D2- and 5-HT2-receptors were found with IC50 values ranging between 2 X 10(-5) and 7 X 10(-5) mol/l. For propranolol binding affinities for alpha 1-, alpha 2-, D1-, D2- and 5-HT2-receptors were found with IC50 values ranging between 2 X 10(-6) and 9 X 10(-5) mol/l.