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.

Conclusion: 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.