MEMBRANE CHLORIDE CONDUCTANCE AND CAPACITANCE IN JURKAT T-LYMPHOCYTES DURING OSMOTIC SWELLING

Video microscopy and whole-cell patch-clamp recording were used to monitor changes in relative cell volume (V/V-0), chloride conductance (g(Cl)), and membrane capacitance (C-m) during osmotically induced swelling in Jurkat T lymphocytes. Cellular swelling was initiated with hyperosmotic pipette solutions. Simultaneous evaluation of V/V-0 and gel revealed a 59-s delay between the inception of swelling and the activation of outwardly rectifying, ATP-dependent Cl- channels. Following the delay, increases in V/V-0 and g(Cl) progressed in parallel. In contrast, C-m, a measure of cell surface area, fell gradually at a rate of approximate to-150 ff/min after whole-cell access was achieved. The decline in C-m lasted 200 s and was followed by a rapid rise (approximate to 750 ff/min). The rise in C-m coincided with a variable increase in ''leak'' current. g(Cl) increased at a slower rate and reached lower peak values in experiments performed without ATP; ATP had no effect on the biphasic C-m time course. The temporal separation of conductance and capacitance during swelling suggests that g(Cl) and C-m vary independently, supporting the hypothesis that a large portion, if not all, of the whole-cell Cl- conductance activated during swelling is provided by volume-sensitive Cl- channels preexisting in the plasma membrane.