Isolated epithelial cells from amphibian urinary bladder express functional gap junctional hemichannels

Exposure of the urinary bladder epithelium of Necturus maculosus (NUB) to p rotease and collagenase yields similar to 50% isolated polarized cells. The se cells express a membrane current slowly activated by depolarization or b y removal of external divalent cations. The biophysical and pharmacological properties of the current are largely consistent with those of gap junctio nal hemichannels. After removal of divalent cations, the cells can also be loaded with 5(6)-carboxyfluorescein, a hydrophilic fluorescent anionic dye, and exposure to dye reduces the current in a manner dependent on membrane voltage and side of application. In contrast, Necturus gallbladder (NGB) ce lls exhibit no membrane conductance attributable to gap junctional hemichan nels, although previous studies reveal the persistence of gap junction plaq ues on the plasma membrane. We conclude that functional gap junctional hemi channels can be expressed on the surface of certain isolated epithelial cel ls and that this is not a necessary consequence of the isolation procedure. These structures may contribute to cell damage under pathological conditio ns involving cell detachment.