title: Na,K-ATPase activity and epithelial interfaces in gills of the freshwater shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).
abstract: Diadromous freshwater shrimps are exposed to brackish water both as an obligatory part of their larval life cycle and during adult reproductive migration; their well-developed osmoregulatory ability is crucial to survival in such habitats. This study examines gill microsomal Na,K-ATPase (K-phosphatase activity) kinetics and protein profiles in the freshwater shrimp Macrobrachium amazonicum when in fresh water and after 10-days of acclimation to brackish water (21 per thousand salinity), as well as potential routes of Na+ uptake across the gill epithelium in fresh water. On acclimation, K-phosphatase activity decreases 2.5-fold, Na,K-ATPase alpha-subunit expression declines, total protein expression pattern is markedly altered, and enzyme activity becomes redistributed into different density membrane fractions, possibly reflecting altered vesicle trafficking between the plasma membrane and intracellular compartments. Ultrastructural analysis reveals an intimately coupled pillar cell-septal cell architecture and shows that the cell membrane interfaces between the external medium and the hemolymph are greatly augmented by apical pillar cell evaginations and septal cell invaginations, respectively. These findings are discussed regarding the putative movement of Na+ across the pillar cell interfaces and into the hemolymph via the septal cells, powered by the Na,K-ATPase located in their invaginations.
authors.affiliation: Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil.
authors.forename: N M
authors.initials: NM
authors.lastname: Belli
authors.forename: R O
authors.initials: RO
authors.lastname: Faleiros
authors.forename: K C S
authors.initials: KC
authors.lastname: Firmino
authors.forename: D C
authors.initials: DC
authors.lastname: Masui
authors.forename: F A
authors.initials: FA
authors.lastname: Leone
authors.forename: J C
authors.initials: JC
authors.lastname: McNamara
authors.forename: R P M
authors.initials: RP
authors.lastname: Furriel
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002499:Centrifugation, Density Gradient; D033364:Decapoda / Q000166:cytology* / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004848:Epithelium / Q000378:metabolism* / Q000648:ultrastructure; D005618:Fresh Water; D005880:Gills / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D008861:Microsomes / Q000737:chemistry / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013395:Sucrose / Q000737:chemistry
chemical_list: D013395:Sucrose; D000254:Sodium-Potassium-Exchanging ATPase