title: Effects of microgravity and tail suspension on enzymes of individual soleus and tibialis anterior fibers.
abstract: Selected enzymes of energy metabolism were measured in random individual fibers of soleus and tibialis anterior (TA) muscles from rats exposed for 2 wk to spaceflight (F) aboard COSMOS 2044 or tail suspension (T) and from synchronous controls. Average size of soleus fibers (dry weight per unit length) was reduced 37% in F and T fibers; there was little change in TA fibers. Enzyme changes were more pronounced in soleus than in TA fibers. Three enzymes characteristic of fast-twitch muscles, pyruvate kinase, glycerol-3-phosphate dehydrogenase, and 1-phosphofructokinase, were elevated in F and T soleus fibers, but changes in phosphofructokinase were not statistically significant. 3-Ketoacid-CoA transferase, characteristic of slow-twitch muscles, did not change significantly in either F or T fibers. Hexokinase, usually moderately higher in slow- than in fast-twitch muscles, increased markedly in both F and T fibers. In TA fibers analyzed for hexokinase, malate dehydrogenase, phosphohexoisomerase, and pyruvate kinase, only hexokinase and malate dehydrogenase showed significant changes. Hexokinase increased 83% in one of two T muscles. Enzyme data for TA fibers typed by myosin adenosinetriphosphatase were more informative: phosphofructokinase, phosphorylase, and glycerol-3-phosphate dehydrogenase were increased in type IIb fibers of either F or T muscles or both. Malate dehydrogenase was not changed in fibers of any type in either F or T muscle.
authors.affiliation: Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: M M
authors.initials: MM
authors.lastname: Chi
authors.forename: R
authors.initials: R
authors.lastname: Choksi
authors.forename: P
authors.initials: P
authors.lastname: Nemeth
authors.forename: I
authors.initials: I
authors.lastname: Krasnov
authors.forename: E
authors.initials: E
authors.lastname: Ilyina-Kakueva
authors.forename: J K
authors.initials: JK
authors.lastname: Manchester
authors.forename: O H
authors.initials: OH
authors.lastname: Lowry
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D004734:Energy Metabolism / Q000187:drug effects; D006593:Hexokinase / Q000378:metabolism; D066298:In Vitro Techniques; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000166:cytology / Q000201:enzymology* / Q000502:physiology; D011770:Pyruvate Kinase / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013026:Space Flight; D013623:Tail / Q000502:physiology*; D014893:Weightlessness / Q000009:adverse effects*
chemical_list: D008291:Malate Dehydrogenase; D006593:Hexokinase; D011770:Pyruvate Kinase; D000251:Adenosine Triphosphatases