Competitive antagonism of isoprenaline-induced cardiac necroses by β-adrenoreceptor blocking agents

Abstract

Histological methods show that low doses of (±)-isoprenaline may produce cardiac necroses in the rat. The percentage of animals with focal necroses was related to the dose within the range 0·005 to 0·5 mg/kg administered subcutaneously. Therefore the heart-damaging effect of isoprenaline as well as the antagonistic effect of β-adrenoreceptor blocking agents could be evaluated quantitatively. Pre-treatment of animals with dichloroisoprenaline, pronethalol and propranolol produced a parallel displacement to the right of the dose-response line for isoprenaline. However, when lesions were already in progress, these agents were without protecting effect.