title: Age-dependent effects of systemic administration of oxytetracycline on the viscoelastic properties of rat tail tendons as a mechanistic basis for pharmacological treatment of flexural limb deformities in foals.
abstract: OBJECTIVE
  To describe the effect of systemically administered oxytetracycline on the viscoelastic properties of rat tail tendon fascicles (TTfs) to provide a mechanistic rationale for pharmacological treatment of flexural limb deformities in foals.
  
  
  METHODS
  TTfs from ten 1-month-old and ten 6-month-old male Sprague-Dawley rats.
  
  
  METHODS
  5 rats in each age group were administered oxytetracycline (50 mg/kg, IP, q 24 h) for 4 days. The remaining 5 rats in each age group served as untreated controls. Five days after initiation of oxytetracycline treatment, TTfs were collected and their viscoelastic properties were evaluated via a stress-relaxation protocol. Maximum modulus and equilibrium modulus were compared via a 2-way ANOVA. Collagen fibril size, density, and orientation in TTfs were compared between treated and control rats.
  
  
  RESULTS
  Viscoelastic properties were significantly decreased in TTfs from 1-month-old oxytetracycline-treated rats, compared with those in TTfs from 1-month-old control rats. Oxytetracycline had no effect on the viscoelastic properties of TTfs from 6-month-old rats. Collagen fibril size, density, and orientation in TTfs from 1-month-old rats did not differ between oxytetracycline-treated and control rats.
  
  
  CONCLUSIONS
  Results confirmed that systemically administered oxytetracycline decreased the viscoelastic properties of TTfs from 1-month-old rats but not those of TTfs from 6-month-old rats. The decrease in viscoelastic properties associated with oxytetracycline treatment does not appear to be caused by altered collagen fibril diameter or organization. The age-dependent effect of oxytetracycline on the viscoelastic properties of tendons may be related to its effect on the maturation of the extracellular matrix of developing tendons.
authors.affiliation: Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Leslie R
authors.initials: LR
authors.lastname: Wintz
authors.forename: Michael
authors.initials: M
authors.lastname: Lavagnino
authors.forename: Keri L
authors.initials: KL
authors.lastname: Gardner
authors.forename: Aleksa M
authors.initials: AM
authors.lastname: Sedlak
authors.forename: Steven P
authors.initials: SP
authors.lastname: Arnoczky
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D001696:Biomechanical Phenomena / Q000187:drug effects; D003094:Collagen / Q000187:drug effects* / Q000378:metabolism; D004548:Elasticity / Q000187:drug effects; D005109:Extracellular Matrix / Q000187:drug effects*; D006736:Horses; D008297:Male; D046529:Microscopy, Electron, Transmission; D010118:Oxytetracycline / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013623:Tail / Q000187:drug effects* / Q000502:physiology; D013710:Tendons / Q000187:drug effects* / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D003094:Collagen; D010118:Oxytetracycline