Chloride channels and salivary gland function.
Fluid and electrolyte transport is driven by transepithelial Cl- movement. The opening of Cl- channels in the apical membrane of salivary gland acinar cells initiates the fluid secretion process, whereas the activation of Cl- channels in both the apical and the basolateral membranes of ductal cells is thought to be necessary for NaCl re-absorption. Saliva formation can be evoked by sympathetic and parasympathetic stimulation. The composition and flow rate vary greatly, depending on the type of stimulation. As many as five classes of Cl- channels with distinct gating mechanisms have been identified in salivary cells. One of these Cl- channels is activated by intracellular Ca2+, while another is gated by cAMP. An increase in the intracellular free Ca2+ concentration is the dominant mechanism triggering fluid secretion from acinar cells, while cAMP may be required for efficient NaCl re-absorption in many ductal cells. In addition to cAMP- and Ca(2+)-gated Cl- channels, agonist-induced changes in membrane potential and cell volume activate different Cl- channels that likely play a role in modulating fluid and electrolyte movement. In this review, the properties of the different types of Cl- currents expressed in salivary gland cells are described, and functions are proposed based on the unique properties of these channels.
Melvin
J E
JE
Center for Oral Biology, Rochester Institute for Biomedical Sciences, University of Rochester Medical Center, New York 14642, USA.
D000042:Absorption; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D001826:Body Fluids / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D004573:Electrolytes / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D018721:Muscarinic Agonists / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000502:physiology; D012463:Saliva / Q000737:chemistry / Q000378:metabolism; D018987:Salivary Ducts / Q000378:metabolism; D012469:Salivary Glands / Q000294:innervation / Q000378:metabolism / Q000502:physiology*; D012636:Secretory Rate / Q000502:physiology; D012965:Sodium Chloride / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000502:physiology
D000318:Adrenergic beta-Agonists; D018118:Chloride Channels; D004573:Electrolytes; D018721:Muscarinic Agonists; D012965:Sodium Chloride; D000242:Cyclic AMP; D002118:Calcium