Cardiomyopathy in crowded rabbits.

Rabbits were crowded 4 to a cage for 2 weeks, then released for 1 week, crowded again for 2 weeks, and so on. Of 44 rabbits subjected to intermittent crowding, only 9 survived for longer than 10 months, 20 died during the 1st month, and 15 died between the 2nd and 9th month of the experiment. Histological sections of the myocardium showed myocytolysis, intersititial edema, and an increased amount of acid mucopoly saccharides in rabbits surviving for 2 weeks and more. The accumulations of acid mucopolysaccharides were apparently unrelated to necrotic foci. Long-term survivors frequently showed myocardial fibrosis and endocardial fibroelastosis, as well as basophilic degeneration of myocardial fibers. The lesions observed were similar to those described in idiopathic endomyocardiopathy in Southern Africa. Therefore, the rabbit may be of some value for research in cardiomyopathies.