Intracellular Cl? concentration in striated intralobular ducts from rabbit mandibular salivary glands

• DOI: 10.1007/bf00585938
• Publication Date: 2004-11-23T02:58:36Z
• Authors: K. R. Lau; R. L. Evans; R. M. Case
• Keywords: Male; 0303 health sciences; Osmolar Concentration; Intracellular Membranes; Mandible; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; In Vitro Techniques; Fluorescence; Salivary Glands; Amiloride; 03 medical and health sciences; Chlorides; Potassium; Quinolines; Animals; Rabbits; HEPES

Intralobular striated ducts have been isolated from rabbit mandibular salivary glands and maintained in primary culture for up to 2 days. Such ducts were loaded with the Cl(-)-sensitive fluorescent dye N-(ethoxycarbonylmethyl)-(6-methoxyquinolinium bromide) (MQAE) and intracellular Cl- concentration ([Cl-]i) monitored using a fluorescence microscope. Intracellular Cl- could be rapidly and reversibly emptied from striated duct cells by replacing Cl- in the superfusing solution with NO(3)-. [Cl-]i could be lowered by removal of external Na+, exposure to 10 microM amiloride or to 10 microM 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). Both amiloride and DIDS were able to inhibit the recovery of [Cl-]i after an initial exposure to Na(+)- or Cl(-)-free solution. The amiloride derivatives, benzamil (2 microM) and N-isobutyl-N-methylamiloride (MIBA), (10 microM) also lowered [Cl-]i by similar amounts as 10 microM amiloride. Varying external K+ concentration ([K+]o) also affected [Cl-]i. Increasing [K+]o increased [Cl-]i, but decreasing [K+]o did not decrease [Cl-]i. Instead, [Cl-]i was also increased when [K+]o was lowered below the control value. Bumetanide (0.1 mM) lowered [Cl-]i by only a small amount, while ouabain (1 mM) had no significant effect on [Cl-]i. These data are consistent with current models of electrolyte transport in salivary ducts which include Cl- channels, Na+ channels, and Na+/H+ exchangers in the apical membrane. The effects of low [K+]o can be interpreted in terms of a K(+)-dependent exit mechanism for Cl-.