Possible neuroendocrine role for oxytocin in bone remodeling.
OBJECTIVE
The present study was carried out to evaluate the assumption that oxytocin (OT) plays a neuroendocrine role in bone remodeling. For this purpose the changes in serum calcium, serum RANKL and OPG levels were detected in addition to morphological examination of the bone.


METHODS
Two regimes for OT administration were used: 1. one group of rats was treated with a high OT dose of 40 microIU/kg b.w. for 6 weeks; 2. second group was treated with a low OT dose of 8 microIU/kg b.w. for a longer period of treatment (12 weeks). To evaluate the possible role of OT in bone remodeling, the changes in serum calcium, serum RANKL (sRANKL--Receptor Activator of Nuclear factor K-beta Ligand) and OPG (Osteoprotegerin) levels were detected and sRANKL/OPG ratio was calculated. To confirm the biochemical data, a histological and ultrastructural study of rat bone samples, before and after injection with oxytocin, was also performed.


RESULTS
In general, the present study shows that intramuscular injection of OT at both concentrations and durations of treatment caused a significant decrease in serum calcium and sRANKL levels and a significant increase in OPG level. The sRANKL/OPG ratio was decreased as well. Morphological observations showed that both OT treatments induced a slight effect on bone remodeling in favor of bone formation.


CONCLUSIONS
Oxytocin was found to posses a growth promoting effects on bone. The results also clearly showed that treatment with a high OT dose for a short duration was more effective than the low dose for a longer period of treatment.
Elabd
S K
SK
Department of Physiology, Alexandria University, Egypt.
Sabry
I
I
Hassan
W B
WB
Nour
H
H
Zaky
K
K
D000818:Animals; D016723:Bone Remodeling / Q000502:physiology*; D002118:Calcium / Q000097:blood; D005269:Femur / Q000187:drug effects / Q000648:ultrastructure; D008297:Male; D010006:Osteoblasts / Q000187:drug effects / Q000648:ultrastructure; D010010:Osteoclasts / Q000187:drug effects / Q000648:ultrastructure; D010011:Osteocytes / Q000187:drug effects / Q000648:ultrastructure; D053244:Osteoprotegerin / Q000097:blood; D010121:Oxytocin / Q000502:physiology*; D053245:RANK Ligand / Q000097:blood; D051381:Rats
D053244:Osteoprotegerin; D053245:RANK Ligand; C506032:Tnfrsf11b protein, rat; D010121:Oxytocin; D002118:Calcium