THE ACTION OF SULFHYDRYL REAGENTS UPON THE ISOLATED FROG HEART

¹ Departments of Pharmacology of Loyola University School of Medicine, Chicago, Illinois, and the Instituto Nacional de Cardiologia, Mexico City, Mexico

The effect of three groups of specific reagents which combine with the -SH groups of the sulfhydryl enzymes has been studied on the frog heart. These groups include: (1) two oxidizing agents, porphyrindin and sodium orthoiodosobenzoate; (2) the alkylating reagent, iodoacetamide; and (3) two mercaptide-forming compounds, sodium para-chloromercuric benzoate and 3-amino, 4-hydroxybenzene arsenous hydrochloride.

All the compounds cause a diminished relaxation of the ventricle which terminates in systolic standstill. In regard to their action upon the frog heart they can be divided into two groups: (1) the oxidizing agents and iodoacetamide, in which the standstill is preceded by an increased amplitude of contraction and a systolic effect resembling the effect of the cardiac glycosides and (2) the mercaptide-forming compounds in which systolic standstill is preceded by a depressant effect caused by a diminished excitability and contractility of the ventricular muscle. In concentrations smaller than those necessary to cause systolic standstill the mercaptide-forming compounds produce a predominantly diastolic effect.

Glutathione protects against the effects of all five reagents, but does not reverse their action.