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Exp Parasitol. 1995 Dec;81(4):546-55.

Echinococcus granulosus: partial characterization of the conductive properties of two cation channels from protoscoleces of the ovine strain, reconstituted on planar lipid bilayers.

Author information

1
Departamento de Química Analítica y Fisicoquímica, Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina.

Abstract

Two cationic channels present in the microsomal fraction from Echinococcus granulosus protoscoleces of the sheep strain were studied in planar bilayer reconstitution experiments. A whole-worm homogenate was subjected to differential centrifugation and the postmitochondrial supernatant was laid on the top of a discontinuous sucrose gradient. The 15-30% (w/v) membrane fraction, enriched in NADPH-cytochrome c reductase, exhibited the highest fusion rate, two cationic channels being most frequently reconstituted. Both of them were highly cation-selective and had high conductances (244 and 107 pS in symmetrical 150 mM KCl). In most experiments, none of them displayed voltage dependence. The 244-pS channel was activated by Ca2+ and blocked by Ba2+, both in the micromolar range, thus partially resembling the Ca(2+)-activated K+ channel from more highly evolved animals. The 107-pS channel exhibited a Cs+ approximately equal to K+ > Na+ > Li+ > Ca2+ selectivity sequence (as measured by permeability ratios) and, most frequently, a high open probability (> 0.9) irrespective of the experimental conditions used, therefore sharing many properties of Schistosoma mansoni outer tegumental membrane cation channels.

PMID:
8542996
DOI:
10.1006/expr.1995.1148
[Indexed for MEDLINE]

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