Chloride conductance is activated by membrane distention of cultured chick heart cells

Abstract

The aim was to apply various maneuvers to perturb the volume of cultured chick cardiac myocytes and to evaluate the association between the swelling-activated chloride conductance and membrane distention. Swelling of single chick heart cells was induced by (1) reduction of external osmolarity; (2) elevation of intracellular osmolarity; (3) isosmotic urea uptake; and (4) positive pressure injection. Changes in cell volume and whole-cell currents were recorded simultaneously and a comparison among differently activated whole-cell currents was made in terms of time course, reversal potential (Erev), whole-cell conductance, and response to a number of channel blockers. Although the time course of cell swelling varied between the different experimental maneuvers, the resultant whole-cell current displayed nearly identical current-voltage relationships: outward rectification and a reversal potential near the calculated chloride equilibrium potential (ECl). The induced currents were inhibited by Cl- channel blockers, diphenylamine-2-carboxylate (DPC) and 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), and were almost completely suppressed by gadolinium. In addition, the Cl- conductance activated by hyposmotic swelling was largely reversed when cell volume was reduced by applying negative pressure through the whole-cell patch pipette. The close relationship between the degree of cell volume increase and current activation suggests that membrane distention induced by cell swelling triggers a Cl(-)-selective conductance in cardiac myocytes.