title: Modulation by K+ Plus NH4+ of microsomal (Na+, K+)-ATPase activity in selected ontogenetic stages of the diadromous river shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).
abstract: We investigate the synergistic stimulation by K(+) plus NH4 (+) of (Na(+), K(+))-ATPase activity in microsomal preparations of whole zoea I and decapodid III, and in juvenile and adult river shrimp gills. Modulation of (Na(+), K(+))-ATPase activity is ontogenetic stage-specific, and particularly distinct between juveniles and adults. Although both gill enzymes exhibit two different sites for K(+) and NH4 (+) binding, in the juvenile enzyme, these two sites are equivalent: binding by both ions results in slightly stimulated activity compared to that of a single ionic species. In the adult enzyme, the sites are not equivalent: when one ion occupies its specific binding site, (Na(+), K(+))-ATPase activity is stimulated synergistically by ≈ 50% on binding of the complementary ion. Immunolocalization reveals the enzyme to be distributed predominantly throughout the intralamellar septum in the gill lamellae of juveniles and adults. Western blot analyses demonstrate a single immunoreactive band, suggesting a single (Na(+), K(+))-ATPase α-subunit isoform that is distributed into different density membrane fractions, independently of ontogenetic stage. We propose a model for the modulation by K(+) and NH4 (+) of gill (Na(+), K(+))-ATPase activity. These findings suggest that the gill enzyme may be regulated by NH4 (+) during ontogenetic development in M. amazonicum.
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
authors.forename: Francisco A
authors.initials: FA
authors.lastname: Leone
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
authors.forename: Thais M S
authors.initials: TM
authors.lastname: Bezerra
authors.affiliation: Departamento de Biologia Molecular, Centro de Ciências Exatas e da Natureza, Universidade Federal da Paraíba, João Pessoa, PB, Brasil.
authors.forename: Daniela P
authors.initials: DP
authors.lastname: Garçon
authors.affiliation: Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
authors.forename: Malson N
authors.initials: MN
authors.lastname: Lucena
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
authors.forename: Marcelo R
authors.initials: MR
authors.lastname: Pinto
authors.affiliation: Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil.
authors.forename: Carlos F L
authors.initials: CF
authors.lastname: Fontes
authors.affiliation: Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
authors.forename: John C
authors.initials: JC
authors.lastname: McNamara
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D000818:Animals; D060829:Arthropod Proteins / Q000378:metabolism*; D005260:Female; D005880:Gills / Q000201:enzymology; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D064587:Osmoregulation; D010042:Ouabain / Q000494:pharmacology; D033541:Palaemonidae / Q000201:enzymology*; D011188:Potassium / Q000502:physiology*; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D045483:Rivers; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D064751:Ammonium Compounds; D060829:Arthropod Proteins; D021122:Protein Subunits; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium