Effects of human parathyroid hormone related protein on osteoporosis of ovariectomized rats

Objective To investigate the therapeutic effects of human parathyroid hormone related protein (PTHrP1-34) on osteoporosis of ovariectomized osteoporotic rats. Methods Sixty 4-month-old female Wislar rats were involved in this study and 40 of them were ovariectomized and another 20 received sham operation. After 6 weeks of ovariectomy the osteoporosis model was confirmed by examing 10 ovariectomized and sham-operated rats. The 30 osteoporotic rats were randomly divided into 3 treatment groups, i.e. PTHrP, estradiol and placebo. Human 40 μg/kg PTHrP1-34 was subcutaneously injected once daily to PTHrP group and the estradiol group was injected with 40 μg/kg estradiol benzoate once every 3 days.The placebo and shamoperated rats were given 0.2 ml saline every 3 days. The bone mineral density (BMD), bone histomorphology, the bone weight of dry and ash and serum Ca,P,alkaline phosphatase (ALP) were measured after 3 months' therapy. Results After 6 weeks of ovariectomy, the lumbar BMD of ovariectomized rats were significantly declined compared with those of the sham-operated rats. After 12 weeks treatment the femoral and lumbar BMD and the rate of bone weight of dry and ash in the PTHrP group were increased obviously compared with those of placebo groups.There was no significant difference between PTHrP group and estradiol group, in PTHrP group the percent age of trabecular area,trabecular width,osteoblast surface and mineral apposition rate were obviously higher than those in placebo group.Conclusion Treatment with 40 μg/kg dose of hPTHrP1-34 administered once daily is effective in treating ovariectomy-induced osteoporosis.