Khajirat Netnee. Effect of ovariectomy and estrogen supplementation on the recovery from exercise-induced muscle injury. Master's Degree(Exercise Physiology ). Mahidol University. : Mahidol University, 2008.
Effect of ovariectomy and estrogen supplementation on the recovery from exercise-induced muscle injury
Abstract:
The aim of this study was to determine the effects of ovariectomy and estrogen
supplement on indices of muscle injury and functional recovery following exercise.
Female Sprague Dawley rats were divided into five groups; sham control (SHAMC),
sham exercise (SHAME), ovariectomized control (OVXC), ovariectomized exercise
(OVXE), and ovariectomized exercise with estrogen supplement (OVXES). In the
exercise groups, injury was induced by a single bout of downhill running (90 min at 17
m/min, 16° inclination), whereas the unexercised groups served as control.
Immediately after and at 3 days and 14 days after injury, soleus muscle was removed
for histological, biochemical, and functional studies.
Results showed that downhill running increased both serum creatine kinase
(p<0.05) and myeloperoxydase activities (p<0.05) compared to the control level
immediately post-injury. Estrogen supplement tended to attenuate this effect especially
during the 3 days post-injury. Muscle wet weights were unchanged among groups but
the muscle wet-to-dry weight ratio increased significantly in the exercised groups
immediately following exercise, and was restored to the baseline value by 14 days of
recovery. Maximal twitch and tetanic forced production were significantly reduced in
exercised rats relative to that of uninjured rats immediately post-exercise. Myofibre
cross-sectional areas (CSA) were similarly reduced in the exercised rats. Estrogen
replacement restored the mean fiber CSA, improved the muscle function, and
increased the numbers of activated satellite cells staining positive for MyoD in all
exercised animals at day 3 of recovery. Cyclo-oxygenase-2 activity of injured soleus
muscle increased significantly (p<0.05) at 3 days following downhill running in
OVXE, but remained the same in OVXES and SHAME groups.
These results suggest that estrogen has a protective effect against injury following
downhill running, increases satellite cells activation, and improves skeletal muscle
strength during recovery. However, this estrogenic effect seems to be independent on
the COX-2 pathway.