Studies on Cardioactive Steroids

Abstract

The potency of 17 derivatives of 16α-gitoxin was tested in the isolated atrium and heart of the guinea pig and the contractility-increasing activity of the 16α-gitoxin 16α-acetate was compared with that of 16α-gitoxin in the anesthetized dog. The potency of 16α-gitoxin was increased by the substitution of 16α-OH for 16α-methyl ether, 16α-acetate and 16α-nitrate. Substitution of the 16α-acetyl group for substituents with a higher molar volume diminished this enhanced potency. Variation in the digitoxose moiety caused an increase or decrease in potency depending on the position and number of the substituted OH groups. In spite of changes in 16α-OH, the low influence on rhythmicity persisted, as was found in experiments in the dog.