Mechanism of uphill chloride transport of the mouse lacrimal acinar cells: studies with Cl- -sensitive microelectrode.

The mechanism of uphill Cl- accumulation by mouse lacrimal acinar cells was studied using double-barrelled Cl- -selective microelectrodes. When measured in standard tris-buffered saline solution, the membrane potential (Vm) was -39.2 +/- 0.4 mV and intracellular Cl- activity (AiCl) was 34.6 +/- 0.7 mmol/l which was 1.4 times higher than the equilibrium level. In Na+-free solution, AiCl decreased from 34 mmol/l to 19 mmol/l in 100 min, a level that was close to the equilibrium activity. Return to the standard solution restored the normal level of AiCl in 5 min. In the presence of furosemide (1 mmol/l), Cl- uptake induced by Na+-readmission was inhibited by 44%. Superfusion with a K+-free solution gradually decreased AiCl until it was close to the equilibrium level after 75 min; superfusion with a high-K+ (29.5 mmol/l) solution increased AiCl significantly. In the presence of ouabain (1 mmol/l), switching the superfusing solutions from K+-free to high-K+ and from high-K+ to K+-free at timed intervals of 15 min caused, respectively, an increase (+9 mmol/l) and a decrease (-7 mmol/l) in AiCl. These changes in AiCl were inhibited by furosemide respectively by 61% and 24%. In the presence of furosemide, DIDS (1 mmol/l) or furosemide plus DIDS, the initial rate of Cl- uptake after cessation of acetylcholine (ACh 1 mumol/l) stimulation was inhibited by 47%, 37% or 74%, respectively. Present results show that the characteristics of the uphill chloride uptake by the mouse lacrimal acinar cells are consistent with those of Na+-K+-Cl- cotransport.(ABSTRACT TRUNCATED AT 250 WORDS)