Patch clamp studies of human placental cytotrophoblast cells in culture

Abstract

Despite the importance of the trophoblast in the exchange of ions across the placenta, little is known of the transport mechanisms for ions in trophoblast cells. We have used patch clamp techniques to study ion channels in human cytotrophoblast cells in culture (days 2–8).In an initial survey, 11 cell-attached and 13 inside-out patches were studied and 13 channels were observed. Of these, the following four channels were identified: a) a large conductance Cl − channel (386±20 pS; n=3) with characteristics typical of maxi Cl − channels (Gogelein, 1988) and previously identified at the microvillous membrane of the human placental syncytiotrophoblast at term (Brown et al., 1993), b) a smaller conductance channel (19.5±1.0 pS; n=3) present in inside-out patches which may be Cl − selective, c) a Ca 2+ activated K + channel with a maximum conductance of 202 pS in cell attached and 182 pS in inside-out patches, and d) a 56 pS channel (maximum conductance at negative potentials of 56±3 pS; n=4) present in cell attached patches which may be selective for K + . The ion selectivities, kinetics, pharmacology, and regulation of the channelshave yet to be studied and their roles in trophoblast transport are unknown at present. Human cytotrophoblast cells in culture provide an ideal system to study the incidence and characteristics of ion channels and how these may change throughout trophoblast differentiation.