Drinking and Na/K-ATPase Alpha-Subunit Isoform Expression in Antarctic Fish

Creighton University, Omaha NE

Investigators

Abstract

Nototheniid fishes inhabiting the near freezing (-2C) waters of McMurdo Sound have some of the highest serum and cellular sodium (Na) concentrations and lowest gill sodium/potassium-ATPase (Na/K-ATPase, the sodium/potassium pump) activities of any marine teleost. The enzyme Na/K-ATPase regulates the Na concentration in the cells of many organisms. Maintaining a high salt content in the cells of these fish lowers the freezing point to allow habitation of cold Antarctic waters and reduces the salt gradient between the fish and the seawater. Based on previous studies of temperature effects, it is hypothesized that Antarctic nototheniids have lower drinking rates, lower salt excretion rates and a higher proportion of the low intracellular Na affinity for a specific subunit of the Na/K-ATPase (a3-isoform) compared to New Zealand nototheniids that inhabit warmer waters. These unique osmoregulatory properties explain the high serum and cellular Na concentrations found in nototheniids south of the Antarctic Polar Front. The proposed studies will compare and contrast the unique osmoregulatory mechanisms of Antarctic nototheniids with those of New Zealand nototheniids with respect to 1) seawater drinking rates and serum and cellular chemical composition of the fish, 2) enzymatic properties and expression pattern of mRNA and protein and 3) temporal and spatial localization of the Na/K-ATPase a3-isoform subunit in the fish gills. To accomplish these objectives four species of nototheniids, representing ecologically diverse habits above and below the Antarctic Polar Front will be studied. The broader impacts of this project include increasing our knowledge about the role of Na-K-ATPase in the cellular function in many organisms, strengthening our understanding of the biochemical and physiological adaptations of the Antarctic nototheniids that allow them to survive and thrive in the ice-laden waters south of the Antarctic Polar Front, providing field and laboratory research experience for graduate and undergraduate students, and significant outreach activities in science education to elementary and high school students and teachers.