A DISTINCT MEMBRANE CURRENT IN RAT LENS FIBER CELLS ISOLATED UNDER CALCIUM-FREE CONDITIONS

PURPOSE. TO investigate whether lens fiber cells isolated and maintain ed under calcium-free conditions exhibit distinct membrane currents. M ETHODS. Fiber cells were isolated from the cortical portion of neonate rat lenses using a trypsin digestion protocol and were maintained in EDTA-buffered Ringer's solutions. Membrane currents were recorded from fiber bundles using the whole-cell patch-clamp technique. RESULTS. Co rtical fiber cells of up to 600-mu m length were viable and amenable t o whale-cell patch-clamp recording. The major current recorded under t hese conditions was a slowly activating, voltage-dependent current tha t was markedly increased on membrane depolarization. This current appe ared to be fiber cell specific and had similar properties to currents elicited by gap junction hemichannels previously recorded by others in Xenopus oocytes. CONCLUSIONS. This is the first report of whole-cell patch-clamp recordings from intact elongated fiber cells. Fiber cells kept in calcium-free bath medium appear to be electrically ''leaky'' a nd exhibit a distinct membrane current that has not been described pre viously for lens cells. This current is unlikely to be active in the n ormal lens but may play a role in the depolarized cataractogenic lens.