Inotropic Activity of a Series of Amino Acids. ∗

Summary

A series of neutral ammo acids (1-leucine, 1-serine, dl-serine, 1-cysteine, 1-methionine, 1-threonine, glycine) consistently produced positive inotropic and pressor responses when administered intravenously and intra-aortically in vagotomized, open-chest dogs. The ability of DCI to decrease the positive inotropic response to the intra-aortic injection of 1-leucine and 1-methionine indicates that adrenergic receptor sites situated in the myocardium are involved. Acute bilateral adrenalectomy also decreased these positive inotropic and pressor responses, suggesting a close interaction between the adrenal system and the circulatory stimulant effects of these agents. The acidic amino acids, 1-aspartic acid and 1-glutamic acid, and the basic amino acid 1-arginine primarily depressed the myocardial force responses, with the blood pressure exhibiting a biphasic response.