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Human skeletal muscle responses to prolonged spaceflight: enzyme and substrate adaptations
Author(s) -
Fitts Robert H,
Colloton Patricia A,
Lim WaiMay,
Riley Danny A,
Bain James L,
Trappe Scott,
Costill David
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a952-c
Subject(s) - phosphofructokinase , citrate synthase , glycogen , medicine , chemistry , endocrinology , cytochrome c oxidase , lactate dehydrogenase , fiber type , biochemistry , skeletal muscle , enzyme , glycolysis , biology
Soleus and gastrocnemius biopsies from 5 astronauts and 5 cosmonauts were obtained preflight and on landing day after 6 months on the International Space Station. Subjects were segregated into those performing more than 200 (HT) or less than 100 (LT) min/wk of treadmill exercise. Post‐flight, the HT group retained histochemical cytochrome oxidase activity and oil red O‐positive lipids in soleus type I fibers. The LT group had type I fibers with less cytochrome oxidase activity and larger reductions in lipids. PAS staining showed increased glycogen content in type I fibers, more pronounced in LT. Citrate synthase (CS), carnitine palmitoyl transferase 1b and phosphofructokinase (PFK) were unchanged immunohistochemically. Single fiber biochemistry revealed no changes in PFK activity. CS activity (mole·kg −1 dry fiber·hr −1 ) was unchanged in the LT group but increased significantly in soleus type I (4.14 ± 0.34 to 6.84 ± 0.23) and gastrocnemius type II (3.26 ± 0.17 to 4.10 ± 0.24) fibers of the HT group. In gastrocnemius type II fibers, lactate dehydrogenase decreased (43.85 ± 2.48 to 33.06 ± 1.87) in HT and increased (22.84 ± 0.90 to 31.00 ± 1.34) in LT. Prolonged spaceflight depleted type I fiber lipids and increased glycogen with greater effect in LT than the HT groups. While metabolic enzymes were relatively unaltered, oxidative marker enzymes were better protected by higher exercise. Supported by NASA Grant NCC9‐116.