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Am J Physiol Gastrointest Liver Physiol 255: G367-G373, 1988;
0193-1857/88 $5.00
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AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 3 367-G373, Copyright © 1988 by American Physiological Society

ARTICLES

Cl(-)-HCO3- antiport in rat lacrimal gland

R. W. Lambert, M. E. Bradley and A. K. Mircheff
Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033.

With the use of analytical subcellular fractionation and tracer uptake methods we have demonstrated the presence of a Cl(-)-HCO3- antiport mechanism in the rat exorbital lacrimal gland. We find that outwardly directed gradients of HCO3- and of 35Cl- accelerated the flux of 36Cl- into isolated membrane vesicles. Because vesicle membrane potentials were clamped to 0 mV with K+-valinomycin, the observed anion gradient-dependent acceleration of Cl- influx could not be attributed to conductive fluxes. The antiporter had an apparent K0.5 for Cl- between 6 and 10 mM. It was sensitive to the stilbene derivatives 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). It was also sensitive to the loop diuretic furosemide, which has frequently been used in tests for NaKCl2 symporter activity. Other anions inhibited anion gradient-driven Cl- influx in the sequence SCN- greater than NO3- greater than Cl- greater than HCO3- greater than SO2-4. The density distribution of Cl(-)-HCO3- antiport activity indicated that approximately 80% of the transporter was associated with intracellular membranes, suggesting the presence of cytoplasmic pools of functional antiporters. Because several studies have already shown the presence of Na+-H+ antiporter activity in lacrimal acinar cell basolateral membranes, a cellular model for lacrimal acinar electrolyte secretion is proposed in which a parallel array of Cl- -HCO3- and Na+-H+ antiporters mediates the Na+-dependent accumulation of Cl- against its electrochemical potential gradient.


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B. Walcott, A. Birzgalis, L. C. Moore, and P. R. Brink
Fluid secretion and the Na+-K+-2Cl- cotransporter in mouse exorbital lacrimal gland
Am J Physiol Cell Physiol, October 1, 2005; 289(4): C860 - C867.
[Abstract] [Full Text] [PDF]


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