Long-term growth hormone-releasing factor administration on growth hormone, insulin-like growth factor-I concentrations, and bone healing in the Beagle.
Twelve 11 month old male Beagles were assigned to two treatment groups: a control group (saline) and a group receiving human growth hormone (GH)-releasing factor (hGRF) [1-29]NH2 (25 micrograms/kg, SC, TID). Treatment was started 6 days prior to surgery (day 1) and continued until necropsy (3 dogs per group/day) on d 29 or 58. Two porous polyethylene rods were surgically implanted on the lateral diaphysis of the femoral shaft and a 3 mm hole was drilled through the cortex between the two implants of each dog on day 1. Blood and urine were collected on d -6, 27 and 56. Human GRF injections produced a significant (P < 0.05) increase in GH release following each injection. An increase in GH response was also observed (P < 0.05) over time. The concentration of insulin-like growth factor-1 (IGF-1) increased for 5 weeks and then reached a plateau. None of the hematologic or urine measured parameters was affected by the treatment (P > 0.05). Albumin, calcium, and protein concentrations were higher (P < 0.05) on d 27 and 56 in GRF-treated animals. Histological sections of the onlay sites showed that bony ingrowth tended to be greater into the porous polyethylene material in GRF-treated animals than the controls at d 28 and 57, while no difference was observed in the degree of periosteal bone formation around the implants at either time period (P > 0.05). Bone formation into the cortical defect was greater in the GRF-treated dogs when compared to controls at day 57 only. In conclusion, chronic hGRF [1-29]NH2 treatment in Beagle dogs produced an increased GH response over time and increased IGF-1 concentrations. It also appeared to promote bony ingrowth into a porous polyethylene onlay and into a bony deficit.
Dubreuil
P
P
College of Veterinary Medicine, St. Hyacinthe, Québec, Canada.
Abribat
T
T
Broxup
B
B
Brazeau
P
P
D000818:Animals; D001835:Body Weight / Q000502:physiology; D001842:Bone and Bones / Q000166:cytology / Q000502:physiology* / Q000601:surgery; D002118:Calcium / Q000097:blood / Q000652:urine; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005269:Femur / Q000166:cytology / Q000502:physiology / Q000601:surgery; D013006:Growth Hormone / Q000032:analysis* / Q000097:blood / Q000652:urine; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000652:urine; D008297:Male; D011095:Polyethylenes; D011506:Proteins / Q000378:metabolism; D012709:Serum Albumin / Q000032:analysis; D013997:Time Factors; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology*
D011095:Polyethylenes; D011506:Proteins; D012709:Serum Albumin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D002118:Calcium