title: Na(+)-K(+)-2Cl(-) cotransporter-mediated fluid secretion increases under hypotonic osmolarity in the mouse submandibular salivary gland.
abstract: Water-handling epithelia are sensitive to the osmotic environment. In this study, the effects of a hypo-osmotic challenge on carbachol (CCh)-induced fluid secretion was investigated using an ex vivo submandibular gland perfusion technique and intracellular pH and Ca(2+) measurements. The osmolality of the perfusion solution was altered to examine the response of the gland to a hypotonic challenge. The flow rate was increased by 34% with a 30% hypotonic solution (225 mosmol/kgH2O), although the Ca(2+) response was unchanged. The lowering of the external Cl(-) by 50% abolished this increase in the 30% hypotonic solution. Furthermore, bumetanide, an inhibitor of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1), completely inhibited the fluid secretion increase caused by the 30% hypotonic solution, and both the total amount of fluid and the flow rate were identical to those of the isotonic solution. This finding was confirmed by measuring the NKCC1 bumetanide-dependent NH4 (+) transport; Na(+)-K(+)-2Cl(-) transport was upregulated >40% by a 30% hypotonic challenge. Therefore, the increase in CCh-induced fluid secretion in response to hypotonic conditions can be attributed, to a large extent, to the specific activation of the NKCC1.
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Kidokoro
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan nakamoto@kyu-dent.ac.jp.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Nakamoto
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Mukaibo
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kondo
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Munemasa
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Imamura
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Masaki
authors.affiliation: Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Hosokawa
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D002034:Bumetanide / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D009994:Osmolar Concentration; D009997:Osmotic Pressure / Q000502:physiology*; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D064506:Solute Carrier Family 12, Member 2 / Q000187:drug effects / Q000378:metabolism*; D013363:Submandibular Gland / Q000378:metabolism*
chemical_list: D049994:Sodium Potassium Chloride Symporter Inhibitors; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; D002217:Carbachol
keywords: NH3-NH4+ prepulse technique; Na+-K+-2Cl− cotransporter; osmolarity; saliva secretion