THE ISOLATION OF A CARDIAC ACTIVE PRINCIPLE FROM MAMMALIAN TISSUE

¹ Laboratory of Kidney and Electrolyte Metabolism and Laboralory of Chemical Pharmacology, National Heart Institute, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare, Bethesda, Maryland

A substance with digitalis-like activity occurring in mammalian blood and tissues has been isolated and identified as -palmitoyl lysolecithin.

Much of the lysolecithin occurs as an inactive precursor, presumably in the form of a hemiacetal derivative of a fatty aldehyde. The substance is unevenly distributed in the body occurring in highest concentration in adrenal medulla and in the heart. Little or none occurs in skeletal muscle.

Its digitalis-like activity has been shown by its effect on the hypodynamic frog heart, on the staircase phenomenon in the isolated frog ventricle, on the tension developed by the right ventricular wall of the squab and the isolated carotid strip of the rabbit.

Two forms of lysolecithin, esterified at the and positions of glycerol were isolated. Of these, the isomer was presumed to be an artefact arising by intramolecular rearrangement of the form during isolation.

-Lysolecithin, which has no digitalis-like activity, was found to be readily hydrolyzed by the phospholipase A of snake venom.