A comparison of growth inhibition of Tetrahymena furgasoni by C19 and C21 steroids.

The growth inhibition of Tetrahymena furgasoni (once known as "T. pyriformis W") by C19 and C21 steroids of similar structure was measured by determining cell population at 24 h and 48 h following addition of the steroid. A cis-fusion of the A/B rings junction, unsaturation at C-1,2, or C-4,5 and carbonyl substitution all enhanced inhibition, whereas the presence of two hydroxyl groups decreased inhibition. The results indicated that the transformation of C19 and C21 steroids by this protozoon may be part of a detoxication mechanism.