RICHARDS, J.G.*; SCHULTE, P.M.; University of British Columbia, Vancouver; University of British Columbia, Vancouver: Metabolic acclimation to hypoxia in Fundulus heteroclitus
Environmental hypoxia has profound effects on pathways involved in ATP production. During periods of acute hypoxia, ATP is primarily produced by �anaerobic� metabolism and there is a down regulation of aerobic metabolism. During acclimation to moderate hypoxia, we hypothesize that changes in gene expression will act to optimize pathways involved in energy supply to reduce oxygen consumption. We choose pyruvate dehydrogenase kinase (PDK) as a candidate gene and examined its expression in Fundulus heteroclitus, a hypoxia tolerant fish, during exposure to moderate hypoxia (0.5 to 0.8 mg O2/L). PDK inhibits pyruvate dehydrogenase (PDH) resulting in decreases in mitochondrial carbohydrate oxidation and lower oxygen demands. Two isoforms of PDK (PDK 2 and 2a) were identified in F. heteroclitus, each with a tissue specific distribution. Our data demonstrate that PDK responds rapidly to hypoxia in F. heteroclitus. Exposure to ~0.8 mg O2/L for 48 h caused a 3 to 4 fold increase in PDK 2 and 2a mRNA in heart. Changes in PDK and PDH activity were also monitored during hypoxia exposure.
