Different adaptations of alpha-actinin isoforms to exercise training in rat skeletal muscles.
OBJECTIVE
Alpha (alpha)-actinins are located in the skeletal muscle Z-line and form actin-actin cross-links. Mammalian skeletal muscle has two isoforms: alpha-actinin-2 and alpha-actinin-3. However, the response of alpha-actinin to exercise training is little understood. Therefore, the current study examined the effects of exercise training on the expression level of two alpha-actinin isoforms in skeletal muscles.


METHODS
Twelve male Wistar rats were assigned randomly to a control (C; n = 6) or exercise training (T; n = 6) group. After T animals were trained on an animal treadmill for 9 weeks, alpha-actinin-2 and alpha-actinin-3 levels in the plantaris, white and red gastrocnemius muscles were analysed. In addition, changes in the myosin heavy chain (MyHC) composition were assessed, and muscle bioenergetic enzyme activities were measured.


RESULTS
Results show that exercise training increased alpha-actinin-2 expression levels in all muscles (P < 0.05). However, no significant difference was found in alpha-actinin-3 expression levels between C and T animals. Subsequent MyHC analyses of all muscle showed an MyHC shift with direction from IIb to IIa. Furthermore, enzymatic analysis revealed that exercise training improved enzyme activities related to aerobic metabolism.


CONCLUSIONS
The results of this study demonstrate that exercise training alters the expression level of alpha-actinin at the isoform level. Moreover, the increase in expression levels of alpha-actinin-2 is apparently related to alteration of skeletal muscle: its aerobic capacity is improved.
Ogura
Y
Y
Department of Physiology, St Marianna University School of Medicine, Kanagawa, Japan.
Naito
H
H
Kakigi
R
R
Akema
T
T
Sugiura
T
T
Katamoto
S
S
Aoki
J
J
D000185:Actinin / Q000378:metabolism*; D000818:Animals; D001835:Body Weight / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000201:enzymology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D025221:Phosphofructokinases / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D020033:Protein Isoforms / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D024744:Skeletal Muscle Myosins / Q000378:metabolism
C498530:Actn2 protein, rat; C530217:Actn3 protein, rat; D020033:Protein Isoforms; D000185:Actinin; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase; D025221:Phosphofructokinases; D006593:Hexokinase; D024744:Skeletal Muscle Myosins; D018995:Myosin Heavy Chains