title: Proton transport and Na+/H+ exchange in vesicles isolated from sockeye salmon (Oncorhynchus nerka) kidneys during migration from salt to fresh water.
abstract: Renal epithelial function, proton flux and sodium stimulated proton flux, was observed in vesicles isolated from the brush border of the proximal tubule of Sockeye Salmon (Oncorhynchus nerka) during migration. Brush border membrane vesicles (BBMV) were isolated from the body kidney of Sockeye Salmon using aggregation/differential centrifugation techniques. Vesicle purity was tested using a series of epithelial and basal lateral markers including alkaline phosphatase, maltase, gamma-glutamyl transferase (GGTP), Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase and the lysosomal marker acid phosphatase. An enrichment/depletion factor for each marker was determined by comparison of purified BBMV with kidney homogenate. Vesicles exhibit an enrichment factor for alkaline phosphatase, GGTP, maltase, Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase. A depletion factor was observed for acid phosphatase. Vesicle integrity was tested by measuring the time course of proton flux in the presence of a pH gradient. Amiloride sensitive sodium stimulated proton flux was observed in these vesicles. The presence of sodium caused a saturable increase in the rate of proton flux, indicating the activity of a sodium/proton antiport protein in BBMV.
authors.affiliation: Department of Chemistry/Physics, University of Alaska Anchorage 99508.
authors.forename: E G
authors.initials: EG
authors.lastname: Holmberg
authors.forename: N
authors.initials: N
authors.lastname: Turner
mesh_terms: D000064:Acclimatization; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D005618:Fresh Water; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism*; D011522:Protons; D012474:Salmon; D012623:Seawater; D017923:Sodium-Hydrogen Exchangers; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D002352:Carrier Proteins; D011522:Protons; D017923:Sodium-Hydrogen Exchangers; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase