Recombinant equine growth hormone does not affect the in vitro biomechanical properties of equine superficial digital flexor tendon

Objective-To evaluate the effect of recombinant equine growth hormone (rEGH) on the in vitro biomechanical properties of normal adult equine superficial digital flexor tendon (SDFT). Study Design-Completely randomized design. Sample Population-Nine Standardbred horses, 6 to 9 years of age with ultrasonographically normal forelimb SDFT. Methods-Six horses were administered intramuscular (IM) rEGH at 10 mug/kg/day for 1 week, and then 20 mug/kg/day for another 5 weeks; 3 horses (control subjects) were administered an equivalent daily volume of sterile water IM. Horses were killed at the end of the 6-week treatment period, and both forelimb SDFT were harvested and stored at -70degreesC. In vitro biomechanical testing was performed under uniaxial tension. Results were analyzed using a general linear model of analysis of variance; significance was set at P < .05. Results-There were no differences in cross-sectional area, maximal load at failure, yield load, ultimate and yield tensile strain, ultimate and yield tensile stress, or stiffness between tendons from control and treated horses. Conclusions-Administration of rEGH to adult Standardbred horses for 6 weeks had no detectable effect on the in vitro biomechanical properties of normal SDFT. Clinical Relevance-Administration of rEGH does not modulate the in vitro biomechanical properties of SDFT from adult Standardbred horses. (C) Copyright 2002 by The American College of Veterinary Surgeons.