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 s tudies in intact placenta. The purpose of this work was to explore the suitability of purified trophoblast plasma membrane as a source of io n channels for reconstitution in artificial lipid membranes. STUDY DES IGN: Human placental brush border membranes were purified by different ial and gradient centrifugation and fused with small liposomes. Giant liposomes were then generated by a cycle of dehydration and rehydratio n. These giant liposomes are suitable for electrophysiologic studies a nd were probed for the presence of active ion channels by the patch-cl amp method. RESULTS: The results reported here indicate the presence o f a high conductance chloride channel showing some similarities with ' 'maxi'' chloride channels described in secreting and absorbing epithel ia. The channel had a slight outward rectification with conductances o f 232 and 300 pS at negative and positive potentials, respectively. CO NCLUSIONS: For the first time successful reconstitution of a human pla cental ion channel is achieved in a system suited for electrophysiolog ic studies. The chloride channel described might play a role in transp lacental transport.