Journal of Applied Physiology, Vol 49, Issue 4 583-588, Copyright © 1980 by American Physiological Society
Functional overload of rat fast-twitch skeletal muscle during development
A. N. Belcastro, H. Wenger, T. Nihei, D. Secord and A. Bonen
The intent of this study was observe the effects of different training
programs on selected biochemical properties in lantaris muscle of young
rats. Littermates (10 days old) were assigned to endurance (E), sprint (S),
and control (C) groups. Animals in each group were partitioned into either
21- or 51-day groups and 10-day controls. Myofibrillar ATPase activities at
21 and 51 days (0.720 +/- 0.028 and 0.719 +/- 0.012 mumol Pi.mg-1.min-1)
were higher than the 10-day activity (0.191 +/- 0.022 mumol Pi.mg-1.min)
for C animals (P less than or equal to 0.05). At 51 days, E training
resulted in a lower ATPase activity than both the 21-day E and 51-day C
animals (P less than or equal to 0.05). Sarcoplasmic reticulum protein
yield and Ca2+ binding and uptake increased from 10 to 51 days for C
animals (P less than or equal to 0.05). The Ca2+-binding ability for 51-day
E animals (26.1 +/- 3.4 nmol Ca2+/mg) was greater than for the 51-day C
animals (20.0 +/- 1.69 nmol Ca2+/mg) (P less than or equal to 0.05). The
plantaris muscle of S animals were not altered at 21 and 51 days compared
to C animals were not altered at 21 and 51 days compared to C animals (all
variables). The results suggest that exercise training alters the
biochemical characteristics of skeletal muscle during growth.
