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 Tetrahy mena pyriformis GL [1, 7, 12, 13]. Nigericin transports K+ across biol ogical membranes along the gradient. This transport is generally equil ibrated 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 int racellular pH of Tetrahymena pyriformis GL by means of two labelled mo lecules: C-14-DMO and H-3-inulin. This measurement of pHi requires pri or knowledge of the number of cells and their volume. The results reve al a correlation of the toxicity of nigericin, acidification of the in tracellular environment and increase in cell volume leading to the ret urn of pHi to control values.