title: Estrogen influences satellite cell activation and proliferation following downhill running in rats.
abstract: To investigate the influence of estrogen on postexercise muscle repair processes, we examined the effects of estrogen supplementation (0.25-mg pellet) on numbers of myofibers positive for markers of total, activated, and proliferating satellite cells in rat skeletal muscles 72 h following downhill running. Ovariectomized female rats (n = 44) were divided into four groups (n = 11 per group): sham (no estrogen) controls (SC); sham, exercised (SE); estrogen-supplemented controls (EC); and estrogen-supplemented, exercised (EE). After 8 days of estrogen exposure, animals were exposed to 90 min of treadmill running at 17 m/min (-13.5 degrees ). Seventy-two hours later, soleus and white vastus muscles were removed and immunostained for total [paired box homeotic gene 7 (Pax7)], [activated myogenic differentiation factor D (MyoD)], and proliferating [5-bromo-2'-deoxyuridine (BrdU)] satellite cells. beta-Glucuronidase activity was increased (P < 0.05) in both muscles following exercise; however, the postexercise elevations in enzyme activity were attenuated in the EE group compared with the SE group in the soleus (P < 0.05). Immunohistochemical analysis revealed that exercised groups displayed increased numbers of myofibers containing total, activated, and proliferating satellite cells compared with control groups (P < 0.05). Furthermore, greater numbers of fibers positive for markers of total, activated, and proliferating satellite cells were observed postexercise in EE animals compared with SE animals for both muscles (P < 0.05). The results demonstrate that estrogen may potentially influence post-damage repair of skeletal muscle through activation of satellite cells.
authors: Dept. of Kinesiology and Physical Education, Wilfrid Laurier Univ., Rm. 517, Bricker Academic Bldg., Waterloo, Ontario, Canada N2L 3C5.
authors: Deborah L
authors: DL
authors: Enns
authors: Peter M
authors: PM
authors: Tiidus
mesh_terms: D000818:Animals; D001835:Body Weight; D049109:Cell Proliferation; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D005260:Female; D005966:Glucuronidase / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D017570:MyoD Protein / Q000378:metabolism; D010052:Ovariectomy; D051763:PAX7 Transcription Factor / Q000378:metabolism; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012420:Running; D032496:Satellite Cells, Skeletal Muscle / Q000201:enzymology / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004343:Drug Implants; D017570:MyoD Protein; D051763:PAX7 Transcription Factor; D004958:Estradiol; D005966:Glucuronidase