Original Article

Effect of intermittent injection of recombinant human parathyroid hormone on bone histomorphometry of ovariectomized rats.

Authors: Ke-Qin ZHANG, Jia-Wei CHEN, Qing-Nan LI, Guang-Fu LI, Xiao-Yun TIAN, Lian-Fang HUANG, Li-Hua BAO, Mei-Lian WANG

Abstract

AIM: To observe the effect of intermittent parathyroid hormone (PTH)
administration on bone histomorphology of relatively old ovariectomized rats.
METHODS: The 6-month-old female SD rats were randomly divided into 5 groups: (1)
sham-operated for baseline (ShamB, n=5), (2)ovariectomized for baseline (OVXB,
n=6), (3) Sham-operated for end point (ShamE, n=6), (4) ovariectomized for end
point (OVXE, n=6), (5) ovariectomized for PTH treatment (OVXEP, n=6). ShamB and
OVXB rats were sacrificed 3 months after operation, ShamE, OVXE and OVXEP rats
were sacrificed 4.5 months after operation. During 3-4.5 months after operation,
OVXEP rats received daily subcutaneous injection of rhPTH1-84, while ShamE and
OVXE received vehicle injection. The proximal tibiae of all rats were processed
without decalcification for quantitative bone histomorphometry.
RESULTS: The percent trabecular area (TbAr) of OVXEP was significantly greater
than that of OVXE (P <0.05), and was similar to that of OVXB (P >0.05), but was
smaller than that of ShamE (P <0.05); the trabecular thickness (TbTh) of OVXEP
was thicker than any other group (all, P <0.05); the trabecular number (TbN) of
OVXEP was only slightly higher than that of OVXE; the percent labeled perimeter
(LPm), mineral apposition rate (MAR) and bone formation rate with bone area as
referent (BFR/BV) of OVXEP were all higher than those of ShamE and OVXE
respectively (P <0.01), whereas the osteoclast number (N of Oc) of OVXEP was
similar to those of ShamE and OVXE (P >0.05).
CONCLUSION: Short-term intermittent injection of rhPTH1-84 can prevent further
bone loss in 9-month-old rats 3 months after ovariectomy, the mechanisms of this
therapy are that PTH could increase TbTh while not alter TbN, and promote
bone-forming activity while not influence bone-resorptive activity.
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