Effect of spaceflight on the maximal shortening velocity, morphology, and enzyme profile of fast- and slow-twitch skeletal muscle fibers in rhesus monkeys.
Weightlessness has been shown to cause limb muscle wasting and a reduced peak force and power in the antigravity soleus muscle. Despite a reduced peak power, Caiozzo et al. observed an increased maximal shortening velocity in the rat soleus muscle following a 14-day space flight. The major purpose of the present investigation was to determine if weightlessness induced an elevated velocity in the antigravity slow type I fibers of the rhesus monkey (Macaca mulatta), as well as to establish a cellular mechanism for the effect. Spaceflight or models of weightlessness have been shown to increase glucose uptake, elevate muscle glycogen content, and increase fatigability of the soleus muscle. The latter appears to be in part caused by a reduced ability of the slow oxidative fibers to oxidize fats. A second goal of this study was to establish the extent to which weightlessness altered the substrate profile and glycolytic and oxidative enzyme capacity of individual slow- and fast-twitch fibers.
Fitts
R H
RH
Department of Biology, Marquette University, Milwaukee, WI, USA.
Romatowski
J G
JG
De La Cruz
L
L
Widrick
J J
JJ
Desplanches
D
D
D000818:Animals; D006003:Glycogen / Q000378:metabolism; D008253:Macaca mulatta; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism; D013026:Space Flight; D014893:Weightlessness
D018994:Myosin Light Chains; D006003:Glycogen; D018995:Myosin Heavy Chains