title: Influence of ovarian hormones on strength loss in healthy and dystrophic female mice.
abstract: OBJECTIVE
  The primary objective of this study was to determine whether strength loss and recovery after eccentric contractions are impaired in healthy and dystrophic female mice with low levels of ovarian hormones.
  
  
  METHODS
  Female C57BL/6 (wild-type) or mdx mice were randomly assigned to ovarian-intact (Sham) and ovariectomized (Ovx) groups. Anterior crural muscles were tested for susceptibility to injury from 150 or 50 eccentric contractions in wild-type and mdx mice, respectively. An additional experiment challenged mdx mice with a 2-wk treadmill running protocol followed by an eccentric contraction injury to posterior crural muscles. Functional recovery from injury was evaluated in wild-type mice by measuring isometric torque 3, 7, 14, or 21 d after injury.
  
  
  RESULTS
  Ovarian hormone deficiency in wild-type mice did not affect susceptibility to injury because the ∼50% isometric torque loss after eccentric contractions did not differ between Sham and Ovx mice (P = 0.121). Similarly, in mdx mice, hormone deficiency did not affect the percent of preinjury isometric torque lost by anterior crural muscles after eccentric contractions (P = 0.952), but the percent of preinjury torque in posterior crural muscles was lower in Ovx than in Sham mice (P = 0.014). Recovery from injury in wild-type mice was affected by hormone deficiency. Sham mice recovered preinjury isometric strength by 14 d (96% ± 2%), whereas Ovx mice maintained deficits at 14 and 21 d after injury (80% ± 3% and 84% ± 2%, P < 0.001).
  
  
  CONCLUSIONS
  Ovarian hormone status did not affect the vulnerability of skeletal muscle to strength loss after eccentric contractions. However, ovarian hormone deficiency did impair the recovery of muscle strength in female mice.
authors.affiliation: Programs in Physical Therapy and Rehabilitation Science, Department of Physical Medicine and Rehabilitation, Medical School, University of Minnesota, Minneapolis, MN.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Kosir
authors.forename: Tara L
authors.initials: TL
authors.lastname: Mader
authors.forename: Angela G
authors.initials: AG
authors.lastname: Greising
authors.forename: Susan A
authors.initials: SA
authors.lastname: Novotny
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Baltgalvis
authors.forename: Dawn A
authors.initials: DA
authors.lastname: Lowe
mesh_terms: D000818:Animals; D003402:Creatine Kinase / Q000097:blood; D005260:Female; D006728:Hormones / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010052:Ovariectomy; D010053:Ovary / Q000378:metabolism*; D011897:Random Allocation; D020127:Recovery of Function / Q000502:physiology; D019415:Torque
chemical_list: D006728:Hormones; D009124:Muscle Proteins; D003402:Creatine Kinase