The polyene antibiotic amphotericin B acts as a Ca2+ ionophore in sterol-containing liposomes.
Amphotericin B (AmB) was shown to induce a Ca2+ influx across ergosterol- and cholesterol-containing large unilamellar liposomes, by following spectrophotometrically the formation of the Arsenazo III-Ca2+ complex. At equivalent antibiotic concentrations the Ca2+ influx was much more extensive through ergosterol-containing membranes (almost 100% with 1 microM AmB, 160 microM lipid) than through cholesterol-containing membranes (below 0.5 microM the influx of Ca2+ was negligible). In the presence of ergosterol-containing membranes the initial rate of Ca2+ influx had the same linear dependence on the ratio antibiotic/lipid whatever the lipid concentration, which was not the case in cholesterol-containing membranes. These results suggest that the channels responsible for the AmB-induced Ca2+ permeability across cholesterol- and ergosterol-containing liposomes have different structures.
Ramos
H
H
Centro de Biologia Celular, Facultad de Ciencias, Universidad Central de Venezuela, Caracas.
Attias de Murciano
A
A
Cohen
B E
BE
Bolard
J
J
D000666:Amphotericin B / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D002784:Cholesterol / Q000494:pharmacology*; D004875:Ergosterol / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology*; D008081:Liposomes / Q000378:metabolism*
D007476:Ionophores; D008081:Liposomes; D000666:Amphotericin B; D002784:Cholesterol; D002118:Calcium; D004875:Ergosterol