Sulfatide and Na+-K+-ATPase: a salinity-sensitive relationship in the gill basolateral membrane of rainbow trout.
We investigated the effect of salinity on the relationship between Na(+)-K(+)-ATPase and sulfogalactosyl ceramide (SGC) in the basolateral membrane of rainbow trout (Oncorhynchus mykiss) gill epithelium. SGC has been implicated as a cofactor in Na(+)-K(+)-ATPase activity, especially in Na(+)-K(+)-ATPase rich tissues. However, whole-tissue studies have questioned this role in the fish gill. We re-examined SGC cofactor function from a gill basolateral membrane perspective. Nine SGC fatty acid species were quantified by tandem mass spectrometry (MS/MS) and related to Na(+)-K(+)-ATPase activity in trout acclimated to freshwater or brackish water (20 ppt). While Na(+)-K(+)-ATPase activity increased, the total concentration and relative proportion of SGC isoforms remained constant between salinities. However, we noted a negative correlation between SGC concentration and Na(+)-K(+)-ATPase activity in fish exposed to brackish water, whereas no correlation existed in fish acclimated to freshwater. Differential Na(+)-K(+)-ATPase/SGC sensitivity is discussed in relation to enzyme isoform switching, the SGC cofactor site model and saltwater adaptation.
Lingwood
D
D
Department of Zoology, University of Guelph, ON N1G 2W1, Canada. dlingwoo@uoguelph.ca
Fisher
L J
LJ
Callahan
J W
JW
Ballantyne
J S
JS
D000222:Adaptation, Physiological; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D005618:Fresh Water; D005880:Gills / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D009994:Osmolar Concentration; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013433:Sulfoglycosphingolipids / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000502:physiology
D013433:Sulfoglycosphingolipids; D000254:Sodium-Potassium-Exchanging ATPase