Digitalis-like biological activity and immunoreactivity in chromatographic fractions of rabbit adrenal extract

Dichloromethane extract of rabbit adrenals was subjected to thin-layer chromatography (Kieselgel 60F-254, MERCK) and digoxin immunoreactivity and digitalis glycoside-like biological activity were determined in the fractions by homogeneous enzymoimmunoassay and by inhibition of 86Rb uptake by red blood cells in vitro, respectively. Both the immunoreactivity and the biological activity maximum were present in two fractions which moved (in chromatography) between the corticosterone and deoxycorticosterone and showed a different RF from the deoxycorticosterone and aldosterone. In association with previous findings on digoxin-like immunoreactivity in the serum of animals with a cardiac overload, the possible existence of a cardiotropic steroid of adrenocortical origin is suggested.