Estrogen effect on post-exercise skeletal muscle neutrophil infiltration and calpain activity

Abstract

We hypothesized that estrogen administration would attenuate skeletal muscle neutrophil infiltration, indices of muscle membrane disruption, and muscle calpain activity shortly after the termination of exercise. Ovariectomized female rats were implanted with either an estogen pellet (25 mg beta-estradiol) or a placebo pellet. Two weeks postimplant, animals were killed either at rest or 1 h after running exercise (60 min at 21 m x min(-1), 12% grade). The 4 experimental groups (n = 12) used were: unexercised placebo (UP), unexercised estrogen (UE), exercised placebo (EP), and exercised estrogen (EE). Blood samples were analyzed for creatine kinase (CK) activity and estradiol content. Plantaris and gastrocnemius muscles were removed and histochemical determination of neutrophil content or biochemical determination of myeloperoxidase (MPO), glucose-6-phosphate dehydrogenase (G6PD), and calpain-like activity determined. Estrogen supplemented animals had 10-20-fold higher circulating estradiol levels than placebo animals. EP animals had significantly higher (P < 0.05) circulating CK activities than EE or unexercised animals. Muscle neutrophil concentrations were significantly (P < 0.01) elevated in EP and EE groups compared with unexercised controls, with EP muscle neutrophil levels also being over 60% greater (P < 0.05) than in EE animals. EP animals also had higher (P < 0.05) muscle MPO activities than unexercised or EE animals. Muscle G6PD activities were not significantly different between any groups. Muscle caplain-like activities were 80% higher (P < 0.01) in EP animals than EE animals with calpain-like activities in EE animals similar to unexercised groups. These results indicate that estrogen supplementation in ovariectomized rats attenuated 1-h post-exercise serum CK activities, muscle neutrophil infiltration, MPO activities, and calpain-like activities when compared with exercised, unsupplemented animals. This supports the possibility of a relationship between estrogen, calpain dependent production of neutrophil chemo-attractant peptides, and 1-h post-exercise skeletal muscle neutrophil infiltration.

Effects of ovarian sex hormones and downhill running on fiber-type-specific HSP70 expression in rat soleus

“…In accordance with our laboratory's previous studies (39,43), serum estrogen concentration in the E animals was approximately eight-to ninefold higher compared with both S and P animals and was at the high end of normal for rodents (23,39,52). The E animals were significantly lighter than both S and P animals, which is believed to be due to differences in insulin-like growth factor-1 and growth hormone release, which are downregulated by estrogen (7,39).…”

“…Animals were returned to their cages and allowed to recover for 8 days before beginning the exercise protocol. We have demonstrated previously that 1 wk of estrogen exposure in this model is sufficient to allow estrogen effects on skeletal muscle to manifest (6,43). This recovery time allowed the pellet-implanted groups to receive prolonged exposure to the ovarian sex hormone.…”

“…Animals were acclimatized for a period of 1 wk in the laboratory before being randomly assigned to one of three treatment groups (n ϭ 16 per group): sham (S), progesterone (P), and estrogen (E). Estrogen (0.25 mg 17␤-estradiol, 21-day time release pellet; Innovative Research of America, Sarasota, FL) and progesterone (25 mg progesterone, 21-day time release pellet, Innovative Research of America) supplementation were administered via subcutaneous pellet implantation (6,43). Briefly, animals were anesthetized via inhaled isoflurane, and a small incision was made in the skinfolds of the neck.…”

“…Progesterone has also been demonstrated to have a role in the inflammatory response (4,9) similar to that of estrogen (42,43), potentially influencing the HSP70 response to a given stress. It is presently unknown if progesterone regulates basal HSP70 expression in skeletal muscle or whether it influences the muscle HSP70 response to exercise in a similar manner to estrogen.…”

Sex differences and estrogen modulation of the cellular immune response after injury

“…P-selectin, CINC-2β, and MCP-1 stayed lowered in the estrogen treated rats 24 hours after injury. The decrease in adhesion molecules and chemokines is modulated by estrogen and could be a result of a reduction of cell-surface integrin expression [57], or reductions of oxidative stress [58][59][60].…”