The action of isoproterenol on the chick embryo heart

Abstract

The action of isoproterenol on the heart of chick embryos has been observed. The drug was injected into the amniotic sac (2 × 80 mg/kg/48 h) from the 5th day of embryonic life up to the time of hatching. The mortality of isoproterenol-treated animals up to day 16 was higher than control animals. Total body oedema (8 to 10 days) and haemorrhagic oedema of the occipital region (10 to 17 days) were observed. From the 5th to the 7th embryonic day malformations of great vessels occurred. From the 7th to the 14th embryonic day a blockade of development of coronary vascularization was regularly observed, particularly in the ventral wall of the right ventricle. This effect was always associated with persistence of intertrabecular spaces in the non-vascularized area, and with a higher water content in the heart. From the 10th to 12th embryonic day, degenerative changes in the cardiac muscle were observed. The lesions were characterized by typical myolysis. Capillaries in the affected area were dilated and blocked with packed erythrocytes. Necrotic changes were localized only in those parts of the ventricular walls in which the vascular bed and myoarchitecture were normally developed. In comparison with similar changes in adults, there was no inflammatory cellular proliferation. It follows from these results that administration of necrogenic doses of isoproterenol to chick embryo causes different types of change at different developmental periods. Each change has a specific, relatively sharply defined and limited critical period.