The effects of bovine recombinant growth hormone administration on insulin-like growth factor-I and the haemopoietic system in thoroughbred geldings.
The effect of intramuscularly administered recombinant bovine growth hormone (rbGH) on insulin-like growth factor-I (IGF-I) and white and red blood cell indices was studied in Thoroughbred geldings. An insulin-like growth factor binding protein (IGFBP)-blocked radioimmunoassay was modified and validated for the measurement of IGF-I in equine blood plasma. Baseline values of IGF-I and blood indices were determined over a 48 h period and then a single dose of 5 microg/kg, 10 microg/kg or 50 microg/kg of rbGH was administered. Insulin-like growth factor-I levels increased in a dose-dependent manner, with the highest values between 12 h and 24 h. The highest dose (50 microg/kg) yielded the greatest IGF-I response with a 90.2+/-10.8% increase at 24 h. White blood cell count increased following the three doses of rbGH with the highest white blood cell count at 12 h after the 50 microg/kg dose. Haemoglobin was significantly increased at 24 h (P< 0.05), when values following doses of 10 microg/kg and 50 microg/kg were significantly greater than after the vehicle or the dose of 5 microg/kg. Red blood cell count was not affected by any of the rbGH doses. These results indicated that rbGH is biologically active in the horse and that rbGH at a dose rate of 10 microg/kg or more could be used therapeutically.
Champion
Z J
ZJ
Research Centre in Reproductive Medicine, Faculty of Medicine and Health Science, The University of Auckland, Auckland, New Zealand. z.champion@auckland.ac.nz
James
E A
EA
Vickers
M H
MH
Breier
B H
BH
Casey
P J
PJ
D000818:Animals; D002417:Cattle; D004906:Erythrocyte Count; D013006:Growth Hormone / Q000031:analogs & derivatives / Q000494:pharmacology*; D006454:Hemoglobins / Q000032:analysis; D006728:Hormones / Q000494:pharmacology; D006736:Horses / Q000502:physiology*; D007273:Injections, Intramuscular; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000378:metabolism; D007958:Leukocyte Count; D008297:Male; D011863:Radioimmunoassay; D011994:Recombinant Proteins / Q000494:pharmacology
D006454:Hemoglobins; D006728:Hormones; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone