Gender-related differences in muscle injury, oxidative stress, and apoptosis.

UNLABELLED: Due to its alleged antioxidant properties, 17beta-estradiol (E2) may protect against muscle injury, oxidative stress, and apoptosis.
PURPOSE: This study sought to determine whether such mechanisms existed between genders for muscle injury, oxidative stress, and apoptosis after eccentric exercise.
METHODS: Eight men and eight women (no oral contraceptive use; midluteal phase of menstrual cycle) performed 7 x 10 eccentric repetitions of the knee extensors at 150% 1RM. Strength, soreness, and blood samples were taken before exercise and 6, 24, 48, and 72 h after exercise while muscle samples were collected before and 6 and 24 h after exercise. Blood samples were assayed for free E2, lactate dehydrogenase (LDH), superoxide dismutase (SOD), and 8-isoprostane (8-iso). Muscle samples were assayed for mitochondrial apoptosis (e.g., bax, bcl-2, cytochrome c, and cell death), total DNA content, and myofibrillar protein content.
RESULTS: Men reported greater soreness levels at 24, 48, and 72 h after exercise, whereas strength changes were similar among genders. At baseline and independent of exercise, females had higher E2 (P < 0.001) and SOD in conjunction with lower 8-iso levels when compared with men. Bax increased in both genders, whereas bcl-2 increased only in women with no cytochrome c changes for either gender after exercise. The bax/bcl-2 ratio in women significantly decreased after 6 h (P = 0.03) and returned to baseline levels after 24 h. Men exhibited greater cell death at all time points (P < 0.05), whereas myofibrillar protein content and total DNA content decreased in both genders at 24 h after exercise. No changes in LDH were found (P > 0.05).
CONCLUSIONS: Although more research is needed, differences between gender may provide greater endogenous protection against oxidative stress and apoptosis.