[Hormonal regulation of cardiac growth: hypothesis with regard to the adrenal cardiotropic steroid].

The myocardium and the adrenals are enlarged simultaneously and the blood endogenic factor, characterized by immunoreactivity, similar to that of digoxin, arises during the cardiac hypertrophy-hyperplasia development, induced by the abdominal aorta ligature or hyperthyrosis. This factor is not identical with corticosterone or aldosterone. Digoxin-similar immunoreactivity and the biological activity were detected in the rabbit and rat adrenocortical chromatographic fractions out of aldosterone, corticosterone, spironolactone and/or desoxycorticosterone zones. The rabbit adrenocortical fraction, having digoxin-similar immunoreactivity and biological activity, stimulates the cardiac cell multiplication in the tissue culture. The cardiac hypertrophy-hyperplasia development, caused by the abdominal aorta ligature or hyperthyrosis, can be prevented by the administration of aminoglutethimide, inhibiting steroidogenesis. Therefore, the endogenic adrenocortical cardiotropic factor. (Called "endocardin" or "endocardiotonin") occurrence and its participation in the cardiac enlargement regulation and proteosynthesis, are considered possible. Chemical structure of this factor is unknown, but some 14-OH steroid derivatives (especially, estradiol) have digoxin-similar immunoreactivity and biological activity. The similar properties were specific to a synthetic (1-24) ACTH, being also detected in the blood of adrenalectomized animals. Since (1-24) ACTH exerts a parallel natriuretic effect, the hypothetic natriuretic hormone may be identical with ACTH or its fragment.