Role of chloride channels in regulating the volume of acinar cells of the rabbit superior lacrimal gland

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Journal Article
Investigative Ophthalmology and Visual Science, 2008, 49 (12), pp. 5517 - 5525
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PURPOSE. To characterize the outward chloride currents (ClOR) in single acinar cells isolated from the rabbit superior lacrimal gland (RSLG) to investigate the hypothesis that ClORmay have a role in regulating the volume of RSLG acini. METHODS. ClORwas characterized by using patch-clamp electrophysiology. Confocal microscopy was used to measure intracellular calcium concentration ([Ca2+]i) and cell volume. Cell volume was altered by superfusing the cells with a hyposmotic solution. RESULTS. The ClORcurrent contributed 33% of total membrane conductance. With normal osmotic conditions, the ClORcurrent was activated by [Ca2+]iwith an EC50of 10-8M. A decrease in intracellular pH from 7.4 to 6.8 totally inhibited ClORcurrent activity. Continuous superfusion of hyposmotic solution caused (1) an increase in cell volume that peaked within 4 minutes and gradually returned to baseline levels after 12 minutes, (2) an increase in [Ca2+]ithat peaked between 6 and 8 minutes and gradually returned to baseline levels after 15 minutes, and (3) an increase the ClORcurrent that peaked within 6 minutes after commencement of perfusion and quickly returned to baseline levels. CONCLUSIONS. The ClORcurrent appears to be triggered by an increase in cell volume and then deactivates within the period of raised [Ca2+]iduring hyposmotic stress, suggesting that ClORmay be an initiating event for volume homeostasis. This effect would be important during RSLG tear secretion, which usually involves cell volume changes and is accompanied by intracellular pH changes in the presence of the raised [Ca2+]ito support secretion. Copyright © Association for Research in Vision and Ophthalmology.
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