Lacrimal gland electrolyte and water secretion in the rabbit: localization and role of (Na+ + K+)‐activated ATPase.

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Abstract
The rate of acetylcholine(ACh)-induced fluid secretion was measured from the main excretory duct of rabbit lacrimal glands perfused in vivo with Krebs Henseleit bicarbonate solutions. Perfusion with ouabain (10-5 M) decreased the rate of lacrimal gland fluid secretion to 23% of the control value. Perfusion with furosemide (10-4 and 10-3 M), which inhibits the coupled transport of Na+ and Cl-, reversibly decreased the rate of secretion to 43 and 33% of the control value, respectively. (Na+ + K+)-activated ATPase was localized in slices of rabbit lacrimal gland using autoradiography with [3H]ouabain. A high density of [3H]ouabain binding sites was present on ductal cells; a very low density was found on acinar cells. For both types of cells the [3H]ouabain binding sites were located on the basolateral plasma membranes. ACh-induced secretion of electrolytes and water is dependent upon (Na+ + K+)-activated ATPase. Coupled transport of Na+ and Cl- appears to be involved in secretion. Basolateral location of the (Na+ + K+)-activated ATPase implies that it plays an indirect role in electrolyte and water secretion. A possible role may be to energize a secondary active transport of Cl- that is mediated by a NaCl cotransport system.