Comparison of the action of BD 40 A and some other beta-adrenoceptor stimulants on the isolated trachea and atria of the guinea pig.

3-Formylamino-4-hydroxy-a-(N-1-methyl-2-p-methoxyphenethyl-aminomethyl)-benzylalcohol hemifumarate (BD 40A) was compared with isoproterenol, orciprenaline, trimetoquinol and salbutamol for its beta-adrenergic activity and selectivity in vitro. On trachea, the maximum relaxing responses to five agonists were similar, but the order of potency was BD 40A greater than trimetoquinol greater than isoproterenol greater than or equal to salbutamol greater than orciprenaline. On atria, the maximum chronotropic and inotropic responses to isoproterenol were greater than those to BD 40A, orciprenaline and trimetoquinol, and salbutamol caused the weakest cardiac stimulating effect. Namely, the latter four drugs appeared to be partial agonists on atria. Salbutamol showed the high selectivity for trachea, whereas orciprenaline and trimetoquinol were equipotent on trachea and atria. Isoproterenol was more potent on atria than on trachea. BD 40A had the highest bronchoselectivity among five agonists and seemed to act on the beta-adrenergic receptor directly.