EPINEPHRINE TOLERANCE OF THE HEART ALTERED BY THYROXINE AND THIOURACIL

CHEMICAL ASSAY OF EPINEPHRINE IN THE RAT HEART

¹ From the Department of Medicine, University of Vermont, College of Medicine, Burlington, Vermont

Injected epinephrine is accumulated in the heart muscle of the rat in a modified form and is readily detectable there by chemical means.

Cardiac death from injected epinephrine is determined by its concentration in the heart muscle. The lethal myocardial concentration was established for the normal rat.

It was found to be distinctly lowered by pretreatment with thyroxine and distinctly elevated by pretreatment with thiouracil. These opposite alterations of the tolerance of the heart to epinephrine were also demonstrated by striking differences in the mortality of thyroxine- and thiouracil-pretreated rats, compared with normal animals, following equal doses of epinephrine.

The clinico-pathological and therapeutic implications of the cardiotoxic effect of epinephrine on the heart sensitized by the thyroid hormone (angina pectoris, sudden cardiac death, etc.), and of the opposite protective effect of thiouracil treatment, are briefly referred to.