Oestrogen receptors mediate oestrogen-induced increases in post-exercise rat skeletal muscle satellite cells.
OBJECTIVE
Our laboratory recently demonstrated that increases in post-exercise muscle satellite cell numbers are augmented by oestrogen. We investigated whether muscle oestrogen receptors (ORs) mediate this effect through administration of an OR antagonist, ICI 182,780.


METHODS
Ovariectomized female rats were divided into three groups: sham, oestrogen (0.25 mg pellet) and oestrogen plus OR blocker (ICI 182,780). Each group was divided into control and exercised groups. ICI 182,780 (5 mg kg(-1) sc) was administered 1 day prior to and 6 days following oestrogen pellet implantation. After 8 days of oestrogen exposure, animals ran downhill for 90 min (17 m min(-1), -13.5 degrees grade) on a treadmill. Soleus and white vastus muscles were removed 24 and 72 h post-exercise and immunostained for total (Pax7), activated (MyoD) and proliferating (BrdU) satellite cells. Muscle damage was indirectly assessed by measuring beta-glucuronidase activity. Two markers (His48 and ED1) of leucocyte infiltration were also examined.


RESULTS
beta-Glucuronidase activities and His48+ and ED1+ leucocytes increased post-exercise, and these increases were attenuated with oestrogen. ICI 182,780 did not influence the attenuating effect of oestrogen on leucocyte infiltration or beta-glucuronidase activities in muscle. Total (Pax7+), activated (MyoD+) and proliferating (BrdU+) satellite cells increased post-exercise, and these increases were augmented with oestrogen. Interestingly, ICI 182,780 abolished both exercise- and oestrogen-mediated increases in these satellite cell markers.


CONCLUSIONS
Oestrogen may augment increases in muscle satellite cells following exercise through OR-mediated mechanisms; furthermore, the attenuation of post-exercise muscle damage and leucocyte infiltration by oestrogen appears to be a non-OR-mediated process.
Enns
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DL
Department of Kinesiology & Physical Education, Wilfrid Laurier University, Waterloo, ON, Canada.
Iqbal
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Tiidus
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PM
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D049109:Cell Proliferation; D004343:Drug Implants; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D000077267:Fulvestrant; D005966:Glucuronidase / Q000032:analysis; D007249:Inflammation; D007962:Leukocytes / Q000502:physiology; D017570:MyoD Protein / Q000032:analysis / Q000378:metabolism; D010052:Ovariectomy; D051761:Paired Box Transcription Factors / Q000032:analysis / Q000378:metabolism; D005082:Physical Exertion; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000378:metabolism*; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism
D015415:Biomarkers; D004343:Drug Implants; D004965:Estrogen Antagonists; D004967:Estrogens; D017570:MyoD Protein; C530821:PAX7 protein, rat; D051761:Paired Box Transcription Factors; D011960:Receptors, Estrogen; D000077267:Fulvestrant; D004958:Estradiol; D005966:Glucuronidase