Isoproterenol-induced necrotic lesions of embryonic heart tissue.

Chick embryos were used for analyzing the effect of isoproterenol on the embryonic heart. Isoproterenol (2 x 80 mg/kg in 48 hrs) was injected into the amniotic sac from the 5th embryonic day to the time of hatching. From the 5th to the 7th embryonic day (ed), transposition of great vessels occurs. From the 7th to the 14th ed, blockade of development of coronary vascularization was regularly observed, particularly in the ventral wall of the right ventricle. This effect is always associated with persistence of intertrabecular spaces in the nonvascularized area and with a higher water content in the heart. From the 10th to the 12th ed, degenerative changes of the cardiac musculature can be observed. 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 where the vascular bed and myoarchitecture were normally developed. In comparison with similar changes in adult specimens, inflammatory cellularization is lacking.