Meeting Abstract

P3.192  Monday, Jan. 6 15:30  Comparative analysis of Na⁺/K⁺ ATPase alpha subunits from the electric organs of weakly electric fish with low and high discharge rates. RIEDMANN, H.L.*; AHADIZADEH, E.N.; MALTBY, R.; MARKHAM, M.R.; The University of Oklahoma; The University of Oklahoma; The University of Oklahoma; The University of Oklahoma hriedmann@ou.edu

Electric fish image their worlds and communicate by generating and sensing electric fields. These electric organ discharges (EODs) are produced by the simultaneous action potentials of electrocytes within the electric organ (EO). Mounting evidence suggests that EOD production incurs significant energetic demands that are larger for species with high EOD rates. The energetic demand of EOD production is attributable largely to Na⁺/K⁺ ATPase activity in the electric organ cells (electroctyes) as the Na⁺/K⁺ ATPase hydrolyzes ATP to actively restore the cell’s ionic gradients in the interval between APs. Functional Na⁺/K⁺ ATPase consist of one alpha and one beta subunit, with the alpha subunit being the primary determinant of pump kinetics. To better understand the relationship of Na⁺/K⁺ ATPase regulation to EOD characteristics, we compared the Na⁺/K⁺ ATPase alpha subunits from the electric organs of Brachyhypopomus gauderio, a fish with irregular low EOD frequencies, and Eigenmannia virescens, a species that generates steady high-frequency EODs. We harvested small sections of EO, extracted total RNA and used RT-PCR followed by 3′- and 5′-RACE to clone and sequence the Na⁺/K⁺ ATPase alpha subunits from the EO of Brachyhypopomus and Eigenmannia. The cDNA clones of > 3300 bp each included a 3027 bp open reading frame encoding a 1009-residue Na⁺/K⁺ ATPase alpha subunit. In both species, the alpha subunits showed amino acid substitutions in functionally significant protein regions, including regions associated with Na⁺ binding and regions known to regulate pump rates. We found higher incidence of amino acid substitutions in functionally important regions of the Eigenmannia Na⁺/K⁺ ATPase.