CHANGE IN INTRACELLULAR PH IN TETRAHYMENA-PYRIFORMIS GL IN RELATION TO THE TOXICITY LEVEL OF THE IONOPHOROUS ANTIBIOTIC NIGERICIN

Nigericin, a carboxylic polyether 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: C-14-DMO and H-3-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.