title: Sex hormone regulation of collagen concentrations in cranial cruciate ligaments of sexually immature male rabbits.
abstract: OBJECTIVE
  To investigate the effects of gonadectomy on collagen homeostasis in cranial cruciate ligaments of male rabbits.
  
  
  METHODS
  30 sexually immature (16-week-old) male New Zealand White rabbits.
  
  
  METHODS
  Rabbits were randomly assigned to 5 groups of 6 rabbits each: sexually intact, placebo (control group); castrated, placebo; castrated, testosterone; castrated, dihydrotestosterone; and castrated, 17β-estradiol (E(2)). Control rabbits underwent a sham operation, and all other rabbits underwent gonadectomy. At the time of gonadectomy, the placebo and sex hormones were administered via slow-release pellets implanted subcutaneously as assigned. After 21 days of hormone supplementation, measurements were obtained of serum testosterone and E(2) concentrations, ligament collagen characteristics, and androgen receptor, estrogen receoptor α, and matrix metalloproteinase expression.
  
  
  RESULTS
  Following gonadectomy and hormone supplementation, the treatment groups differed in serum testosterone and E(2) concentrations to various degrees. Collagen concentrations were lower and fiber diameters higher in the absence of sex hormones, in association with the degrees of estrogen receptor a and androgen receptor expression. Although differences were detected among the groups in matrix metalloproteinase expression, these differences were not significant.
  
  
  CONCLUSIONS
  Sex hormones appeared to play a role in cranial cruciate ligament homeostasis in male rabbits. Physiologic changes triggered by the lack of sex hormones following gonadectomy in sexually immature rabbits may potentially predispose those rabbits to orthopedic injuries.
authors: Department of Anatomy, Auburn University, Auburn, AL 36849, USA. akingbt@auburn.edu
authors: Victoria A
authors: VA
authors: Light
authors: Ron D
authors: RD
authors: Montgomery
authors: Benson T
authors: BT
authors: Akingbemi
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000502:physiology*; D015153:Blotting, Western / Q000662:veterinary; D003094:Collagen / Q000502:physiology*; D004396:Coloring Agents / Q000737:chemistry; D013196:Dihydrotestosterone / Q000097:blood; D004958:Estradiol / Q000097:blood; D012739:Gonadal Steroid Hormones / Q000097:blood / Q000378:metabolism*; D006706:Homeostasis; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D009919:Orchiectomy / Q000009:adverse effects / Q000662:veterinary*; D011817:Rabbits / Q000502:physiology* / Q000601:surgery*; D011863:Radioimmunoassay / Q000662:veterinary; D011897:Random Allocation; D011944:Receptors, Androgen / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D012741:Sexual Maturation; D013739:Testosterone / Q000097:blood
chemical_list: D004396:Coloring Agents; D012739:Gonadal Steroid Hormones; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D003094:Collagen; D020782:Matrix Metalloproteinases