[Endogenous digitalis]

During the past 10 years, several groups of researchers from different laboratories have carried out research on an endogenous substance or substances which had cross immunoreacted to digoxin antibodies in patients without previous cardiotonic treatment. The increase has been demonstrated in various clinical cases which involve an augmentation of plasmatic volume. A considerable amount is known about its molecular structure and anatomic origin; the competitive inhibition of the sodium pump being quite clear.