Chloride channels in the eel intestine

Patches of freshly isolated epithelial cells from eel Anguilla anguilla intestine bathed by the same solution on both sides in the cell-attached configuration had conductances of 57.0+/-1.8 pS (for positive voltages) and 13.3+/-0.7 pS (for negative voltages) (means +/- s.e.m., N=25). Electrical activity was spontaneous in the cell-attached configuration, but was frequently lost after excision. In inside-out patches, channel activity was restored by strong hyperpolarization (-150 mV for 5 s) or depolarization (+150 mV for 5 s). Channel activity was inhibited by the Cl- transport blocker DIDS (1 mmol l-1). The membrane potential measured using the nystatin slow whole-cell technique in primary cultured eel intestine epithelial cells was -35.4+/-1.0 mV (N=14), similar to the expected equilibrium potential for Cl- (-38.2 mV). Removal of Cl- from the bath or application of DIDS caused 16 mV and 6-7 mV depolarizing shifts in reversal potential, respectively. In one experiment, DIDS also induced a reduction in cell conductance from 0. 011+/-0.014 to 0.002+/-0.005 nS. The addition of 0.5 mmol l-1 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (a membrane-permeable analogue of cyclic AMP) to the bath caused an increase in conductance without affecting the reversal potential.