A chloride channel from human placenta reconstituted into giant liposomes.
OBJECTIVE
Ion channels play important roles in epithelial transport, but they are difficult to access for conventional electrophysiologic studies in intact placenta. The purpose of this work was to explore the suitability of purified trophoblast plasma membrane as a source of ion channels for reconstitution in artificial lipid membranes.


METHODS
Human placental brush border membranes were purified by differential and gradient centrifugation and fused with small liposomes. Giant liposomes were then generated by a cycle of dehydration and rehydration. These giant liposomes are suitable for electrophysiologic studies and were probed for the presence of active ion channels by the patch-clamp method.


RESULTS
The results reported here indicate the presence of a high conductance chloride channel showing some similarities with "maxi" chloride channels described in secreting and absorbing epithelia. The channel had a slight outward rectification with conductances of 232 and 300 pS at negative and positive potentials, respectively.


CONCLUSIONS
For the first time successful reconstitution of a human placental ion channel is achieved in a system suited for electrophysiologic studies. The chloride channel described might play a role in transplacental transport.
Riquelme
G
G
Department of Physiology and Biophysics, School of Medicine, University of Chile, Santiago.
Stutzin
A
A
Barros
L F
LF
Liberona
J L
JL
D000469:Alkaline Phosphatase / Q000378:metabolism; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D018118:Chloride Channels / Q000502:physiology*; D004553:Electric Conductivity; D005260:Female; D006801:Humans; D008081:Liposomes; D008564:Membrane Potentials; D008871:Microvilli / Q000502:physiology; D010920:Placenta / Q000648:ultrastructure*; D011247:Pregnancy
D018118:Chloride Channels; D008081:Liposomes; D000469:Alkaline Phosphatase