UBC Theses and Dissertations
Interspecific variation in hypoxia-induced changes in sodium-potassium ATPase activity in marine sculpins (family Cottidae) Shariati, Setareh
Surviving hypoxia exposure requires the reorganization of physiological processes to reduce overall metabolic rate and ATP consumption. Na⁺/K⁺ATPase (NKA), an enzyme found in all animal cell membranes is crucial for the maintenance of cellular homeostasis and is a major consumer of ATP. Some hypoxia-tolerant species are reported to actively downregulate gill NKA during hypoxia. To date, however, no studies have attempted to determine if there is a relationship between specifies-specific hypoxia tolerance and the regulation of NKA during hypoxia. Focusing on the role of NKA in hypoxia survival, the goals of my thesis were to: first, investigate the interspecific relationship between hypoxia tolerance and the hypoxia-induced changes in NKA activity among six species of marine sculpin (family Cottidae); and second, to investigate whether AMP-activated protein kinase (AMPK) plays a role in regulating NKA in tidepool sculpins (Oligocottus maculosus). I measured NKA activity in six sculpin species exposed to hypoxia over 72 hours. Out of all species examined, only the most hypoxia tolerant species (tidepool sculpin) showed the predicted downregulation and only in gill tissue. In the brain, contrary to my prediction to see a decrease in NKA activity, I observed an increase in two species and no directional pattern overall. I found no evidence for a relationship between hypoxia tolerance (as measured by Pcrit) and NKA downregulation. I further investigated the mechanism of NKA regulation in tidepool sculpin gills. I hypothesized that in tidepool sculpins, AMPK (an important protein for cellular energy sensing and regulation) regulates changes in NKA activity. I predicted that exposing tidepool sculpins to AICAR, a pharmacological activator of AMPK would result in a decrease in NKA activity compared to control, but my results did not reveal any evidence in support of this hypothesis. Overall, I showed that there are interspecific differences in how NKA activity is affected by hypoxia exposure in these species, and that NKA downregulation as a hypoxic response exists in the gill of tidepool sculpin but not across the board in marine sculpins. My work also provides new insights into the mechanism of NKA regulation in tidepool sculpins.
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