Triparanol inhibition of Tetrahymena, and its prevention by lipids

Triparanol and its citrate inhibited the growth of Tetrahymena pyriformis mating type II, variety 1, in a chemically defined medium, and synchronous division of strain GL in an inorganic medium. Inhibition of growth was prevented by sterols and by some long-chain fatty acids (oleic, palmitic, stearic), supplied alone and in combinations. The specificity of the responses to the various sterols tested suggests that in this ciliate triparanol impairs the reduction of the 24(25) double bond of sterols such as zymosterol and desmosterol, and the 24(28) double bond of sterols like 24-methylene cholesterol and fucosterol, during conversion of these sterols to ciliate sterol(s). Inhibition of the first synchronous division was prevented by a variety of oleic acid-containing compounds, but not by sterols, so sterol synthesis may not be neces sary for completion of the first synchronous generation. The activity of some long-chain fatty acids (particularly oleic acid) in annulling triparanol toxicity indicates a role of the drug in the metabolism of these compounds.