Estrogen Influence On Myogenic Satellite Cells Following Downhill Running In Male Rats

Abstract

This study examined the effect of estrogen supplementation in rats on myogenic satellite cell quantities in type I and type II muscles following eccentric exercise. Gonad intact adult male rats divided into four groups, estrogen supplemented (25 mg estrogen pellet) control (EC), estrogen supplemented, exercised (EE), sham (no estrogen) control (SC) and sham, exercised (SE). After 1 wk of estrogen exposure the EE and SE animals performed 90 min of intermittent (5 min running/2 minrest) downhill running (−13.5° incline, 17 m/min). 72 hr later exercised (EE and SE) and control (EC and SC) animals were sacrificed and blood samples and soleus and white (superficial) vastus muscles surgically removed. Histochemical sections of soleus and white vastus muscles were examined for myogenic satellite cell content by use of Pax7 antibody and for neutrophil content by use of hematoxylin and eosin (H and E) staining procedures. Downhill running resulted in significant elevations in satellite cells and neutrophils detected in both soleus and white vastus muscle samples (P < 0.01). Interestingly, estrogen supplementation resulted in significantly greater (P < 0.01) post-exercise elevations in satellite cells detected in both soleus and white vastus muscle samples compared to sham (no estrogen) rats. Increases in neutrophils were significantly (P < 0.05) attenuated in estrogen supplemented rats relative to sham in soleus but not in white vastus muscles. Hence, estrogen supplementation in male rats accentuated the 72 hr post-downhill running increase in Pax7 detected myogenic satellite cell number in both soleus and white vastus muscles relative to unsupplemented rats. The mechanisms and physiological consequences of this effect are yet to be determined.