MODIFICATIONS OF PH AND K-ALBICANS BLASTOSPORES INDUCED BY AMPHOTERICIN-B - A P-31 NMR AND K+ ATOMIC-ABSORPTION STUDY( GRADIENTS IN CANDIDA)

Candida albicans blastospores harvested from 8 h (exponential) or 48 h (stationary) cultures were incubated with increasing doses of amphote ricin B (AmB). The time course of H+ influx and K+ efflux was monitore d by in vivo P-31 NMR and K+ atomic absorption respectively. AmB was s hown to be more active on exponential phase cells than on stationary p hase cells. For both growth phases, K+ leakage ocurred before pH acidi fication. In light of these results, together with iodoacetate experim ents, it seems difficult to assert that K+ leakage is a secondary effe ct resulting from an increase in the permeability to protons, as forme rly proposed. In addition, no H+ over K+ selectivity of pores formed b y AmB could be detected. Finally, some unexpected results were afforde d by P-31 NMR experiments: a broadening of Pi signals was detected on exponential phase cell spectra when the blastospores were incubated wi th 10(-3) and 10(-4) M AmB reflecting a transient heterogeneity of the intracellular pH within the cell population. For stationary phase bla stospores, two subpopulations (IIa and IIb) were detected; population IIb, with a more acidic pH(i), was much more sensitive to AmB action.