Administration of bovine, porcine and equine growth hormone to the horse: effect on insulin-like growth factor-I and selected IGF binding proteins.
This study investigated the biochemical effects of administration of three types of recombinant growth hormone (GH; somatotropin) to the Thoroughbred horse. Equine or bovine or porcine GH was administered at a recommended dosage to 3-5-year old Thoroughbred geldings, for up to 21 days. It was shown that, in addition to equine GH, bovine and porcine GH were active in the horse; however, porcine GH caused injection-site reactions that were so serious that administration had to be terminated. The concentrations of a range of GH-related serum protein markers were determined before, during and after the administration period. Because of the short half-life of GH itself, the objective was to identify GH-related markers that showed changes in concentration and which could be used as indicators of the abuse of these hormones. Among the possible markers identified, serum total insulin-like growth factor (IGF)-I was shown to be the most promising, increasing to 270% of the basal concentration for equine GH administration. After GH administration, IGF-I took longer to attain baseline concentrations than the time required for GH concentrations to recover to normal. The concentration obtained from the administration significantly exceeded natural concentrations for IGF-I, as was determined from a population of more than 2000 Thoroughbred horses in three continents. The concentrations of serum free IGF-I and IGF binding protein 3 (IGFBP-3) were also shown to be significantly affected by equine and bovine GH.
De Kock
S S
SS
The Laboratory of the Jockey Club of Southern Africa, PO Box 74439, Turffontein 2140, South Africa.
Rodgers
J P
JP
Swanepoel
B C
BC
Guthrie
A J
AJ
D000818:Animals; D015415:Biomarkers / Q000097:blood; D002417:Cattle; D013006:Growth Hormone / Q000494:pharmacology*; D006736:Horses / Q000378:metabolism*; D019382:Human Growth Hormone / Q000494:pharmacology; D015592:Immunoradiometric Assay; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D011897:Random Allocation; D013045:Species Specificity; D013552:Swine
D015415:Biomarkers; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone