FIG. 7.

GC1 is dispensable for resting skeletal muscle mitochondrial ATP synthesis and content. Mitochondrial ATP generation and oxygen consumption in hind limb skeletal muscles of anesthetized WT and GC1^−/− mice were simultaneously measured by in vivo ³¹P magnetic resonance and optical spectroscopy. (A) Mitochondrial ATP synthesis, which is directly proportional to ATPase activity. (B) Mitochondrial oxygen consumption rate. (C) Mitochondrial ATP synthesis efficiency as determined from the P/O coupling ratio, where P (ATP generation) is divided by oxygen consumption rate (O). (D) Mitochondrial ATP synthesis capacity (ATPmax). (E) Phosphocreatine-to-ATP ratio. For (A–E), n = 9–10 for WT and 10–11 for GC1^−/− groups, respectively. (F) Representative Western blot and densitometric quantitation of mitochondrial marker VDAC1 expression in tibialis anterior muscles. n = 5 for WT and GC1^−/− groups. (G) Representative Western blot and densitometric quantitation of mitochondrial respiratory complex subunit expression in tibialis anterior muscles. (H) Quantitation of PGC1α transcript expression by qPCR. For (G, H), n = 6 for WT and GC1^−/− groups.