The effect of recombinant equine growth hormone on the biomechanical properties of healing superficial digital flexor tendons in horses.
OBJECTIVE
To evaluate the effect of recombinant equine growth hormone (rEGH) on the in vitro biomechanical properties of healing superficial digital flexor tendon (SDFT) in horses.


METHODS
Completely randomized design.


METHODS
Twelve Standardbred horses, 3 to 7 years of age, with ultrasonographically normal forelimb SDFT.


METHODS
One week after induction of collagenase (2,000 U) induced superficial flexor tendonitis, horses were randomly divided into groups of 6. One group was administered intramuscular rEGH (10 microg/kg/day for 1 week, then 20 microg/kg/day for 5 weeks), whereas the other group (control subjects) were administered an equivalent volume of saline (0.9% NaCl) solution. At the end of this 6-week treatment, horses were killed and one forelimb SDFT from each horse was harvested for biomechanical testing under uniaxial tension. Results were analyzed using an unpaired Student's t test; significance was set at P <or=.05.


RESULTS
SDFT from horses treated with rEGH had significantly larger mean cross-sectional areas and lower mean values for ultimate and yield tensile stress, whereas tendons from the control group were biomechanically stiffer than those from the rEGH-treated horses.


CONCLUSIONS
Administration of rEGH to horses for 6 weeks, 1 week after collagenase induced injury to the SDFT, resulted in a significant increase in tendon cross-sectional area, a concomitant reduction in ultimate and yield tensile stress, and reduced tendon stiffness.


CONCLUSIONS
Using this model of tendonitis, rEGH had a negative effect on the biomechanical properties of equine SDFT in the early phases of healing. Based on our results, administration of rEGH to treat superficial flexor tendonitis cannot be recommended.
Dowling
Bradley A
BA
University Veterinary Centre, University of Sydney, Australia.
Dart
Andrew J
AJ
Hodgson
David R
DR
Rose
Reuben J
RJ
Walsh
William R
WR
D000818:Animals; D001696:Biomechanical Phenomena; D017364:Collagenases; D005260:Female; D005552:Forelimb; D013006:Growth Hormone / Q000008:administration & dosage / Q000627:therapeutic use*; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007273:Injections, Intramuscular / Q000662:veterinary; D008297:Male; D052256:Tendinopathy / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary*; D013708:Tendon Injuries / Q000188:drug therapy / Q000662:veterinary*; D013710:Tendons / Q000187:drug effects; D016896:Treatment Outcome; D014945:Wound Healing / Q000187:drug effects* / Q000502:physiology
D013006:Growth Hormone; D017364:Collagenases