In the face of hypoxia: myoglobin increases in response to hypoxic conditions and lipid supplementation in cultured Weddell seal skeletal muscle cells

A key cellular adaptation to diving in Weddell seals is enhanced myoglobin concentrations in their skeletal muscles, which serve to store oxygen to sustain a lipid-based aerobic metabolism. The aim of this study was to determine whether seal muscle cells are inherently adapted to possess the unique skeletal muscle adaptations to diving seen in the whole animal. We hypothesized that the seal skeletal muscle cells would have enhanced concentrations of myoglobin de novo that would be greater than those from a C2C12 skeletal muscle cell line and reflect the concentrations of myoglobin observed in previous studies. In addition we hypothesized that the seal cells would respond to environmental hypoxia similarly to the C2C12 cells in that citrate synthase activity and myoglobin would remain the same or decrease under hypoxia and lactate dehydrogenase activity would increase under hypoxia as previously reported. We further hypothesized that beta-hydroxyacyl CoA dehydrogenase activity would increase in response to the increasing amounts of lipid supplemented to the culture medium. Our results show that myoglobin significantly increases in response to environmental hypoxia and lipids in the Weddell seal cells, while appearing similar metabolically to the C2C12 cells. The results of this study suggest the regulation of myoglobin expression is fundamentally different in Weddell seal skeletal muscle cells when compared with a terrestrial mammalian cell line in that hypoxia and lipids initially prime the skeletal muscles for enhanced myoglobin expression. However, the cells need a secondary stimulus to further increase myoglobin to levels seen in the whole animal.