Change in intracellular pH in Tetrahymena pyriformis GL in relation to the toxicity level of the lonophorous antibiotic nigericin.

Nigericin, a carboxylic poly ether antibiotic, is toxic towards Tetrahymena pyriformis GL [1, 7, 12, 13]. Nigericin transports K(+) across biological membranes along the gradient. This transport is generally equilibrated by an influx of H(+) ions. The toxicity of nigericin (at low 10 mg · l(-1) and high 30 mg · l(-1) levels) was studied by measuring the intracellular pH of Tetrahymena pyriformis GL by means of two labelled molecules: (14)C-DMO and (3)H-inulin. This measurement of pHi requires prior knowledge of the number of cells and their volume. The results reveal a correlation of the toxicity of nigericin, acidification of the intracellular environment and increase in cell volume leading to the return of pHi to control values.