Effects of ovariectomy and estrogen on skeletal muscle function in growing rats.
This study examined the effect of estrogen replacement on soleus muscle size and contractile function in ovariectomized rats during physiological growth. Seven week old female Sprague-Dawley rats were assigned to one of three treatment groups: (1) control animals (SHAM), (2) ovariectomized animals without estrogen replacement (OVX/CO), and (3) ovariectomized animals with 17 beta-estradiol replacement (OVX/E2). OVX/CO and OVX/E2 animals were pair-fed to SHAM animals to rule out the potentially confounding effect of differences in food intake. Rats were sacrificed 4 weeks after surgery and the soleus muscle was removed for analysis. Estrogen replacement reduced body weight, relative body weight gain, and soleus muscle fiber size despite all groups having a similar food intake. Ovariectomy alone had no effect on any of these parameters suggesting that estrogen may inhibit skeletal muscle growth when it is the only ovarian hormone present. Neither ovariectomy nor estrogen replacement affected maximal specific isometric force. Estrogen replacement increased half relaxation time. Ovariectomy resulted in a reduction in time to peak tension that was reversed with estrogen replacement. This reduction was not accompanied by a change in myosin heavy chain composition implying that calcium handling may have been altered. Results from this study suggest that estrogen affects skeletal muscle growth and twitch kinetics.
McCormick
Kathleen M
KM
Department of Exercise and Nutrition Sciences, University of Buffalo, State University of New York, Buffalo, New York 14214, USA. kmccorm@buffalo.edu
Burns
Kellie L
KL
Piccone
Christy M
CM
Gosselin
Luc E
LE
Brazeau
Gayle A
GA
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004435:Eating; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000502:physiology; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014599:Uterus / Q000187:drug effects
D004967:Estrogens; D004958:Estradiol; D018995:Myosin Heavy Chains