RESUMEN
Antioxidant supplementation has been suggested to prevent exercise-induced muscle injury, but the findings are inconsistent. The objective of this study was to investigate the potential protective role of vitamin E treatment against eccentric exercise-induced muscle injury by examining morphological and functional alterations in rat soleus muscle after downhill running as well as muscle injury markers in the blood. Sixty adult male Wistar rats were randomly assigned to vitamin E-treated or placebo-treated groups studied at rest, immediately post-exercise or 48 h post-exercise (n = 10 per group). Vitamin E was administered by daily intraperitoneal injections of 100 mg/kg body mass of DL: -α-tocopheryl acetate for five consecutive days prior to exercise, resulting in the doubling of its plasma concentration. Downhill running resulted in significant (P < 0.05) changes in all injury markers for the placebo-treated rats at 0 and 48 h post-exercise. However, significantly smaller soleus muscle single-twitch tension (P (t)) and unfused (40 Hz) tetanic force, and greater plasma creatine kinase (CK) and lactate dehydrogenase (LD) activities compared with the control were found only immediately post-exercise for the vitamin E-treated rats (P < 0.05). Maximal tetanic force (P (o)) did not decline significantly compared to sedentary controls at neither time points measured. The vitamin E-treated rats had significantly (P < 0.05) higher soleus muscle P (t) immediately post-exercise than the placebo-treated rats as well as lower plasma CK and LD activity 48 h post-exercise. However, there was no difference in P (o) decline between groups at either time points measured. Vitamin E-treated rats had less pronounced morphological alterations in muscle in the immediate and 48-h post-exercise period. In conclusion, the effect of short-term vitamin E supplementation against eccentric exercise-induced muscle injury did not appear to be physiologically significant, because vitamin E failed to prevent the decline in the functional measure of P (o) compared to the placebo conditions.
Asunto(s)
Suplementos Dietéticos , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/lesiones , Carrera/lesiones , Vitamina E/farmacología , Animales , Antioxidantes/administración & dosificación , Antioxidantes/farmacología , Esquema de Medicación , Masculino , Enfermedades Musculares/dietoterapia , Enfermedades Musculares/etiología , Postura/fisiología , Distribución Aleatoria , Ratas , Ratas Wistar , Carrera/fisiología , Factores de Tiempo , Vitamina E/administración & dosificaciónRESUMEN
The ovariectomized (OVX) rat model was used to investigate the effects of estrogen treatment on soleus muscle functionality in situ following muscle injury induced by downhill running. Fifty immature, 24- to 26-d-old, OVX rats were randomly assigned to 5 separate experimental groups: sedentary controls (OVX-Sed), placebo-treated and studied immediately after exercise (OVX-Pb0), placebo-treated and studied 72 h after exercise (OVX-Pb72), estradiol-treated and studied immediately after exercise (OVX-Ed0), and estradiol-treated and studied 72 h after exercise (OVX-Ed72). At the age of 9 weeks, under ketamine and xylazine anesthesia i.p., the rats were subcutaneously implanted with either placebo or 17beta-estradiol-impregnated pellets (0.05 mg/pellet, 3 week release). Treatment with 17beta-estradiol increased the estradiol plasma levels in OVX animals to those normally seen during the proestrous cycle of normal animals. Three weeks after the implantation the rats were subjected to a 90 min intermittent downhill running protocol. Our results indicate that the exercise protocol used in the study induced injury in the soleus muscle, as it was detected by the significant reduction in unfused (stimulation at 10, 20, and 40 Hz) and maximal (Po) tetanic force, as well as the decreased ability of the soleus muscle to maintain tension (stimulation at 40 Hz for 3 min) in OVX-Pb0 and OVX-Pb72 placebo-treated animals subjected to downhill running (injured muscles) as compared with OVX-Sed control rats (uninjured muscle). Estradiol replacement in OVX rats partially protected the soleus muscle from the injury normally induced by downhill running. As compared with the OVX-Pb0 and OVX-Pb72 placebo-treated groups, the soleus muscles of OVX-Ed0 and OVX-Ed72 estradiol-treated rats were capable of producing significantly greater unfused tetanic force and had an increased ability to maintain tension after fatigue. However, estrogen at the dose administered did not prevent the decrease in maximal tetanic force. We postulate that the protective effect of estrogens on muscle strength may be related to the ability of estrogen hormones to attenuate the E--C coupling failure and (or) the disorganization of the contractile apparatus associated with eccentric exercise through a mechanism or mechanisms yet to be fully understood.