title: Tissue hyperoxygenation promotes oxidative metabolism in motor unit.
abstract: Some mutant hemoglobin (Hb) variants are found with lowered O2 affinity. Low oxygen affinity is reported to increase the O2 availability in peripheral tissues (Kunert et al. [1996] Microvasc. Res. 52:58-68). In the present study, we used a mouse model carrying two low-affinity Hb variants, Titusville and Presbyterian, to evaluate the chronic in vivo influence of lowered oxygen affinity on the neuromuscular system. Our model mice showed an increased voluntary running ability compared with wild-type littermates. In the tibialis anterior (TA) muscle of mutant mice, the glycolytic fibers were converted to oxidative ones in where the activity of the mitochondrial marker enzyme succinate dehydrogenase (SDH) was up-regulated. We report that the spinal ventral horn motoneurons innervating TA skeletal fibers also showed higher mitochondrial oxidative enzyme activity. This phenomenon was evidenced by increased SDH activity and electron microscopic (EM) mitochondrial electronic density in these motoneurons. Our data suggest that, as the result of adaptation to the tissue hyperoxygenation, energy metabolism in the neuron-muscle motor unit is augmented and thus function of the motor unit is promoted.
authors.affiliation: Department of Molecular Gerontology, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo, Japan.
authors.forename: Fei
authors.initials: F
authors.lastname: Huang
authors.forename: Takahiko
authors.initials: T
authors.lastname: Shimizu
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ishihara
authors.forename: Shigeki
authors.initials: S
authors.lastname: Yuasa
authors.forename: Kinya
authors.initials: K
authors.lastname: Nishimura
authors.forename: Toyoki
authors.initials: T
authors.lastname: Kugimiya
authors.forename: Takuji
authors.initials: T
authors.lastname: Shirasawa
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D002772:Cholera Toxin / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D005914:Globins / Q000378:metabolism; D006454:Hemoglobins / Q000235:genetics / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D008854:Microscopy, Electron / Q000379:methods; D008931:Mitochondria, Muscle / Q000201:enzymology / Q000648:ultrastructure; D009046:Motor Neurons / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000201:enzymology / Q000294:innervation / Q000502:physiology*; D009154:Mutation; D010100:Oxygen / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013126:Spinal Nerve Roots / Q000166:cytology* / Q000201:enzymology; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013997:Time Factors
chemical_list: D006454:Hemoglobins; D012333:RNA, Messenger; C052635:cholera toxin, B subunit-horseradish peroxidase; D005914:Globins; D002772:Cholera Toxin; D006735:Horseradish Peroxidase; D013385:Succinate Dehydrogenase; D000251:Adenosine Triphosphatases; D010100:Oxygen