INTRACELLULAR PH MODULATES THE ACTIVITY OF CHLORIDE CHANNELS IN ISOLATED LACRIMAL GLAND ACINAR-CELLS

The effects of intracellular pH (pH(i)) on Ca2+-activated Cl- currents in rat lacrimal gland acinar cells were examined. Cl- currents were recorded by conventional whole cell patch-clamp methods using K+-free and Na+-free solutions. pH(i) was varied by using electrode solutions with pH at 6.8, 7.3, or 7.8, and Ca2+ activity was buffered at 100 nM with ethylene glycol-bis(P-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Increasing pH from 6.8 to 7.8 was found to increase whole cell currents. The currents observed exhibited time-dependent activation at depolarizing potentials and time-dependent inactivation at hyperpolarizing potentials (pH 7.8). This behavior is characteristic of Ca2+-activated Cl- channels in lacrimal gland cells. The selectivity of the current was examined at pH 7.8 by removing Cl- from the hath solution. This maneuver caused a positive shift in the reversal potential, as expected for a Cl--selective current. Thus increasing pH(i) appears to activate Ca2+-activated Cl- channels. The possibility that an increase in pH(i) may help sustain Cl- channel activity during secretory activity is discussed.