Steroid mechanisms affecting yeast permeability and viability.

A synthetic aza-cholestane amine was found to be rapidly lethal to Saccharomyces cerevisiae. Lethal action was prevented by pretreating cells with 10m uranyl nitrate. Sublethal concentrations of the steroid prevented the uptake of glucose and alanine. This demonstrated one means by which the steroid affected cell permeability, limiting the growth of the organism. Decreases in viability were related to increases in 260 and 280 mmu absorbing materials. Uranyl protection of viability was found to be related to cellular retention of the ultraviolet-absorbing materials. The steroid, dequadin acetate, and cetyl pyridinium chloride were comparable in lethal action and in causing the leakage of cytoplasmic constituents. Loss of viability and cytoplasmic excretion were detected within minutes after cells were exposed to the steroid. The rate or degree of metabolism of glucose by resting cells did not appear to influence steroid action or the sensitivity of the cells to the steroid.