Modifications of pH and K+ gradients in Candida albicans blastospores induced by amphotericin B. A 31P NMR and K+ atomic absorption study.
Candida albicans blastospores harvested from 8 h (exponential) or 48 h (stationary) cultures were incubated with increasing doses of amphotericin B (AmB). The time course of H+ influx and K+ efflux was monitored by in vivo 31P NMR and K+ atomic absorption respectively. AmB was shown to be more active on exponential phase cells than on stationary phase cells. For both growth phases, K+ leakage occurred before pH acidification. In light of these results, together with iodoacetate experiments, it seems difficult to assert that K+ leakage is a secondary effect resulting from an increase in the permeability to protons, as formerly proposed. In addition, no H+ over K+ selectivity of pores formed by AmB could be detected. Finally, some unexpected results were afforded by 31P NMR experiments: a broadening of Pi signals was detected on exponential phase cell spectra when the blastospores were incubated with 10(-3) and 10(-4) M AmB reflecting a transient heterogeneity of the intracellular pH within the cell population. For stationary phase blastospores, two subpopulations (IIa and IIb) were detected; population IIb, with a more acidic pHi, was much more sensitive to AmB action.
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Laboratoire de Chimie Organique Biologique, (CNRS URA 485), Université Blaise Pascal, Aubière, France.
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Delort
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D000666:Amphotericin B / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000037:antagonists & inhibitors; D006863:Hydrogen-Ion Concentration; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D011188:Potassium / Q000378:metabolism*; D013054:Spectrophotometry, Atomic; D013172:Spores, Fungal / Q000187:drug effects / Q000378:metabolism
D007461:Iodoacetates; D000666:Amphotericin B; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D011188:Potassium; D019807:Iodoacetic Acid