Progesterone and estrogen influence postexercise leukocyte infiltration in overiectomized female rats

Limited research has been conducted on the effects of progesterone alone, or in combination with estrogen, on leukocyte infiltration in skeletal muscle following exercise. To investigate the effects of these female sex hormones, ovariectomized female rats were divided into 4 exercise and 4 control groups: sham, estrogen, progesterone, and a combination of estrogen plus progesterone. Following 8 days of hormone replacement and 24 h postexercise, soleus (red) and superficial (white) vastus muscles were removed and immunostained for His48 (neutrophil)- and ED1 (macrophage)-positive cells. The postexercise increase in leukocyte infiltration was completely (p < 0.05) attenuated with estrogen supplementation alone in both muscle types, relative to sham. Progesterone treatment alone also resulted in a smaller (20%-30%) but significant (p < 0.05) attenuation of postexercise muscle leukocyte infiltration. The combination of estrogen and progesterone treatment did not significantly alter the attenuation seen with estrogen supplementation alone. Hence, progesterone can independently attenuate postexercise muscle leukocyte infiltration, albeit to a lesser degree than estrogen, and it will not negate or accentuate the effect of estrogen.