title: Control of ion transport by mitochondrion-rich chloride cells of eurythermic teleost fish: Cold shock vs. cold acclimation.
abstract: Seawater-acclimated eurythermic mummichogs (Fundulus heteroclitus L.) were acclimated to cold and warm conditions (5 and 20 °C, 4 weeks). Opercular epithelia (OE) from 20 °C-acclimated animals, containing numerous mitochondrion-rich chloride cells were mounted in Ussing-style membrane chambers, cooled to 16, 13, 10, 5 and 2.5 °C, then subjected to hypotonic shock that normally inhibits Cl(-) secretion (as short-circuit current, I(sc)). Cold exposure to 10 °C slowed Cl(-) secretion (Q(10)=1.62 ± 0.204 95% CI) and OEs responded rapidly and reversibly to hypotonic shock, but below 8.0 °C a sharp decrease (Q(10)=5.63 ± 0.736) occurred and the tissue was unresponsive to hypotonicity. By immunocytochemistry, Focal Adhesion Kinase (FAK) phosphorylated at tyrosine-407 (pY(407)) colocalized with CFTR in apical membrane and dephosphorylated with hypotonic shock at 20 °C but failed to dephosphorylate at 5 °C, while opercular epithelia from cold-acclimated fish at 5 and 20 °C responded normally to hypotonic shock. Cold-shock of warm-acclimated OEs also stimulated covering over of mitochondrion- rich cell apical crypts, detected by SEM. Cold-acclimation increased C18:1 and decreased C18:0 fatty acids in liver, indicating homeoviscous adaptation. Eurythermic fish acclimate osmoregulatory systems to cold by maintaining membrane fluidity and preserving complex transport regulation pathways.
authors.affiliation: Department of Biology, St. Francis Xavier University, Antigonish, NS, Canada B2G 2W5.
authors.forename: H E C
authors.initials: HE
authors.lastname: Buhariwalla
authors.forename: E M
authors.initials: EM
authors.lastname: Osmond
authors.forename: K R
authors.initials: KR
authors.lastname: Barnes
authors.forename: R R F
authors.initials: RR
authors.lastname: Cozzi
authors.forename: G N
authors.initials: GN
authors.lastname: Robertson
authors.forename: W S
authors.initials: WS
authors.lastname: Marshall
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D002452:Cell Count; D002712:Chlorides / Q000378:metabolism*; D003080:Cold Temperature; D004594:Electrophysiology / Q000379:methods; D004848:Epithelium / Q000378:metabolism / Q000502:physiology; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005399:Fishes / Q000378:metabolism / Q000502:physiology*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D023781:Fundulidae / Q000378:metabolism / Q000502:physiology; D007038:Hypotonic Solutions / Q000378:metabolism; D017136:Ion Transport; D008297:Male; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000502:physiology; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D002712:Chlorides; D005227:Fatty Acids; D007038:Hypotonic Solutions; D051416:Focal Adhesion Protein-Tyrosine Kinases