Protective effect of isoprenaline pretreatment on the cardiotoxic effect of the same drug.

The study deals with the development of increased resistance of the rat myocardium to ISO-induced injury after pretreatment with the same drug. Reduced sensitivity already developed after the first dose of ISO, whose effect was only slightly increased by subsequent repeated doses. The development of myocardial injury was completed significantly sooner in pretreated animals, and this resulted in a decrease of the extent of the lesion. The reduction of cardiotoxic effect of ISO could be achieved by pretreatment with very small doses of ISO (0.01 mg/kg). An increase in the pretreatment dose augmented the protective effect and, in particular, prolonged the duration of reduced sensitivity. The effect of pretreatment in older animals, which responded to ISO by greater damage, was more pronounced.