title: Gender-related differences in muscle injury, oxidative stress, and apoptosis.
abstract: Due to its alleged antioxidant properties, 17beta-estradiol (E2) may protect against muscle injury, oxidative stress, and apoptosis.
  
  
  OBJECTIVE
  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.
authors.affiliation: Applied Biochemistry and Molecular Physiology Laboratory, Health and Exercise Science Department, University of Oklahoma, Norman, OK, USA.
authors.forename: Chad
authors.initials: C
authors.lastname: Kerksick
authors.forename: Lem
authors.initials: L
authors.lastname: Taylor
authors.forename: Alison
authors.initials: A
authors.lastname: Harvey
authors.forename: Darryn
authors.initials: D
authors.lastname: Willoughby
mesh_terms: D017209:Apoptosis; D001707:Biopsy, Needle; D001823:Body Composition; D004247:DNA / Q000378:metabolism; D015237:Dinoprost / Q000031:analogs & derivatives / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D004958:Estradiol / Q000097:blood / Q000502:physiology; D015444:Exercise; D005260:Female; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000293:injuries* / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress; D012737:Sex Factors; D013482:Superoxide Dismutase / Q000097:blood
chemical_list: D009124:Muscle Proteins; C075750:8-epi-prostaglandin F2alpha; D004958:Estradiol; D004247:DNA; D015237:Dinoprost; D007770:L-Lactate Dehydrogenase; D013482:Superoxide Dismutase