Estrogen Attenuation of Post‐Exercise Muscle Leukocyte Infiltration is not Receptor Mediated

Abstract

Previous work from our laboratory has demonstrated that estrogen will attenuate leukocyte infiltration into skeletal muscle following eccentric exercise. However the mechanisms by which estrogen exerts its effects are still uncertain. We investigated the role of estrogen receptors (ER) on muscle leukocyte infiltration following eccentric exercise through administration of the ER antagonist ICI 182,780 following downhill running to ovariectomized female rats with (E+) or without (E−) estrogen supplementation. At 24 and 48 h post‐exercise, soleus and white vastus muscles were removed and immunostained for HIS 48 (neutrophil) and ED1 (macrophage) positive cells. The increase in number of fibres positive for HIS 48 in soleus and positive for ED1 in the soleus and white vastus was significantly attenuated (p<0.05) in E+ relative to E− rats at 24 hours post‐exercise. E+ rats administered the ER agonist also had significantly (p<0.05) attenuated 24 h post‐exercise increases in HIS 48 and ED1 positive soleus and white vastus muscle fibres similar (p>0.05) to those without ER antagonist. This suggests that the ability of estrogen to attenuate post‐exercise leukocyte infiltration into skeletal muscle is not ER‐mediated.Supported by NSERC Canada