Effects of prolonged exposure to and physical training in hypobaric conditions on skeletal muscle morphology and metabolic enzymes in rats

Adaptations of skeletal muscle morphology and metabolic enzymes were studied after prolonged training in and exposure to hypobaric (740 -770 mbar) as well as normobaric conditions in rats performing treadmill running training for 10, 21 and 56 days. Animals sacrificed after 91 days served as recover...

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Bibliographic Details
Published in:Pflügers Archiv 1996-05, Vol.432 (1), p.50-58
Main Authors: Perhonen, M, Takala, T E, Kovanen, V
Format: Article
Language:English
Subjects:
Acclimatization
Altitude
Animals
Atmospheric Pressure
Body Weight
Male
Muscle Fibers, Skeletal - ultrastructure
Muscle, Skeletal - anatomy & histology
Muscle, Skeletal - enzymology
Organ Size
Physical Education and Training
Physical Endurance
Rats
Rats, Wistar
Space life sciences
Time Factors
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Summary:Adaptations of skeletal muscle morphology and metabolic enzymes were studied after prolonged training in and exposure to hypobaric (740 -770 mbar) as well as normobaric conditions in rats performing treadmill running training for 10, 21 and 56 days. Animals sacrificed after 91 days served as recovery groups from training and hypobaric exposure for 56 days. The rats were divided into normobaric sedentary (NS) and training (NT) groups and hypobaric sedentary (HS) and training (HT) groups. The weights of extensor digitorum longus (EDL) and soleus (SOL) muscles increased significantly in the 56HS and the 56HT groups compared with the 56NS group, the increase being greatest in the 56HS group. No differences in the mean fibre areas (MFA) of these muscles could be seen, whereas clearly reduced MFAs of type IIA and IIB were observed in the tibialis anterior (TA) muscle. However, fibre area distribution analyses in the EDL and TA muscles showed a higher proportion of larger fibers in the 56HS and 56HT groups than in the respective normobaric groups. On the contrary, in SOL muscles the proportion of smaller fibers was higher in the hypobaric than in normobaric groups at 56 days. Increased activities of citrate synthase and beta-hydroxyacyl-CoA-dehydrogenase in SOL and TA muscles in the 56HT group indicate an increase in oxidative capacity. It is concluded that exposure to, and training in moderate hypobaric conditions leads to a positive muscle protein balance which is reflected in increased muscle weights. However, the sites of increased protein synthesis and the possible hyperplasia remain to be studied further.
ISSN:0031-6768
1432-2013
DOI:10.1007/s004240050104