Observations on isoprenaline-induced myocardial necroses

Isoprenaline hydrochloride in subcutaneous doses of 2 × 10 to 2 × 680 mg/kg caused histologically detectable, characteristic heart necroses. Pathological changes were dose-dependent. The degree of necrosis was assessed by a quantitative histological method based on counting the changed morphological elements. The heart necroses due to 2 × 40 mg/kg of isoprenaline were significantly inhibited by pretreatment with different monoamine oxidase inhibitors (iproniazid, a derivative of hydrazine and pargyline and E-250 of the non-hydrazine type, all at 7 × 50 mg/kg intraperitoneally); their severity was significantly increased by reserpine (7.5 mg/kg/48 hr subcutaneously) and guanethidine (2 × 30 mg/kg subcutaneously). In these effects an important role is attributed to respective changes in catecholamine levels.