Properties of two multisubstate Cl- channels from human syncytiotrophoblast reconstituted on planar lipid bilayers

C. Grosman, M. I. Mariano, J. P. Bozzini, I. L. Reisin

Research output: Contribution to journalArticlepeer-review

Abstract

We describe the first successful reconstitution of placental ionic channels on planar lipid bilayers. An apical plasma membrane-enriched vesicle fraction from human syncytiotrophoblast at term was prepared by following isotonic agitation, differential centrifugation, and Mg2+-induced selective precipitation of nonapical membranes, and its purity was assessed by biochemical and morphological marker analysis. We have already reported that, unlike previous patch-clamp studies, nonselective cation channels were incorporated in most cases, a result consistent with the higher permeability for cations as compared with Cl- and with the low apical membrane potential difference at term revealed by fluorescent probe partition studies, and microelectrode techniques. In this paper, we report that Cl--selective channels were incorporated in 4% of successful reconstitutions (14 out of 353) and that their analysis revealed two types of activity. One of them was consistent with a voltage-dependent, 100-pS channel while the other was consistent with the lateral association of 47-pS conductive units, giving rise to multibarrelled, DIDS-sensitive channels of variable conductance (300 to 650 pS). The latter displayed a very complex behavior which included cooperative gating of conductive units, long-lived substates, voltage-dependent entry into an apparent inactivated state, and flickering activity. The role of the reported Cl- channels in transplacental ion transport and/or syncytium homeostasis remains to be determined.

Original languageEnglish (US)
Pages (from-to)83-95
Number of pages13
JournalJournal of Membrane Biology
Volume157
Issue number1
DOIs
StatePublished - 1997
Externally publishedYes

Keywords

  • Apical plasma membrane
  • Cl channels
  • Cooperativity
  • Multiple conductance levels
  • Placenta
  • Single-channel recording
  • Vesicles

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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