Mathers 2017 J Comp Physiol B
|Mathers KE, McFarlane SV, Zhao L, Staples JF (2017) Regulation of mitochondrial metabolism during hibernation by reversible suppression of electron transport system enzymes. J Comp Physiol B 187:227-34.|
Abstract: Small hibernators cycle between periods of torpor, with body temperature (Tb) approximately 5 °C, and interbout euthermia (IBE), where Tb is approximately 37 °C. During entrance into a torpor bout liver mitochondrial respiration is rapidly suppressed by 70 % relative to IBE. We compared activities of electron transport system (ET-pathway) complexes in intact liver mitochondria isolated from 13-lined ground squirrels (Ictidomys tridecemlineatus) sampled during torpor and IBE to investigate potential sites of this reversible metabolic suppression. Flux through complexes I-IV and II-IV was suppressed by 40 and 60 %, respectively, in torpor, while flux through complexes III-IV and IV did not differ between torpor and IBE. We also measured maximal enzyme activity of ET-pathway enzymes in homogenized isolated mitochondria and whole liver tissue. In isolated mitochondria, activities of complexes I and II were significantly lower in torpor relative to IBE, but complexes III, IV, and V did not differ. In liver tissue, only activity of complex II was suppressed during torpor relative to IBE. Despite the significant differences in both ET-pathway flux and maximal activity, the protein content of complexes I and II did not differ between torpor and IBE. These results suggest that the rapid, reversible suppression of mitochondrial metabolism is due to regulatory changes, perhaps by post-translational modification during entrance into a torpor bout, and not changes in ET-pathway protein content.
Labels: MiParea: Respiration, Comparative MiP;environmental MiP
Stress:Temperature Organism: Other mammals Tissue;cell: Liver Preparation: Intact cells, Isolated mitochondria Enzyme: Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase
Coupling state: LEAK, OXPHOS Pathway: N, S, DQ, CIV, ROX HRR: Oxygraph-2k