Inhibition of Growth of Tetrahymena piriformis by Certain Steroids

Abstract

The growth of Tetra-hymena piriformis W is inhibited by several steroids of mammalian origin. The degree of inhibition is related to the molecular configuration. All of the effective growth inhibitors were of the carbon-21 or pregnane series. Hydroxyl substitution at carbon-11 enhanced inhibition, while hydroxyl substitution at carbon-17 lowered the potency of inhibition. The inhibition of growth induced by these steroids was antagonized by stigmasterol or cholesterol. The mode of action of these compounds is discussed with regard to possible competitive inhibition with some metabolite essential for this organism.