title: Na⁺,K⁺-ATPase activity in the posterior gills of the blue crab, Callinectes ornatus (Decapoda, Brachyura): modulation of ATP hydrolysis by the biogenic amines spermidine and spermine.
abstract: We investigated the effect of the exogenous polyamines spermine, spermidine and putrescine on modulation by ATP, K⁺, Na⁺, NH₄⁺ and Mg²⁺ and on inhibition by ouabain of posterior gill microsomal Na⁺,K⁺-ATPase activity in the blue crab, Callinectes ornatus, acclimated to a dilute medium (21‰ salinity). This is the first kinetic demonstration of competition between spermine and spermidine for the cation sites of a crustacean Na⁺,K⁺-ATPase. Polyamine inhibition is enhanced at low cation concentrations: spermidine almost completely inhibited total ATPase activity, while spermine inhibition attained 58%; putrescine had a negligible effect on Na⁺,K⁺-ATPase activity. Spermine and spermidine affected both V and K for ATP hydrolysis but did not affect ouabain-insensitive ATPase activity. ATP hydrolysis in the absence of spermine and spermidine obeyed Michaelis-Menten behavior, in contrast to the cooperative kinetics seen for both polyamines. Modulation of V and K by K⁺, Na⁺, NH₄⁺ and Mg²⁺ varied considerably in the presence of spermine and spermidine. These findings suggest that polyamine inhibition of Na⁺,K⁺-ATPase activity may be of physiological relevance to crustaceans that occupy habitats of variable salinity.
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Ribeirão Preto, Avenida Bandeirantes 3900, Ribeirão Preto, SP 14040-901, Brazil.
authors.forename: Daniela P
authors.initials: DP
authors.lastname: Garçon
authors.forename: Malson N
authors.initials: MN
authors.lastname: Lucena
authors.forename: Juliana L
authors.initials: JL
authors.lastname: França
authors.forename: John C
authors.initials: JC
authors.lastname: McNamara
authors.forename: Carlos F L
authors.initials: CF
authors.lastname: Fontes
authors.forename: Francisco A
authors.initials: FA
authors.lastname: Leone
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D003386:Brachyura / Q000201:enzymology*; D002412:Cations / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005880:Gills / Q000187:drug effects / Q000201:enzymology*; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011073:Polyamines / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology
chemical_list: D002412:Cations; D011073:Polyamines; D013096:Spermine; D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D013095:Spermidine