摘要：Background and Objective: Serum calcium (Ca) is maintained at a balanced level under normal circumstances by a homeostatic system. When the serum Ca level is high, the excess will be deposited in the bone; however, if the serum Ca level is low, Ca will be resorbed from the bone and Ca absorption in the intestine will be increased. As a result, serum Ca metabolism can affect bone morphometry characteristics and Ca status in the body. The aim of this study was to investigate the effect of a nano-calcium phosphate diet on osteoporotic rats after ovariectomy. Experiments were conducted to analyse the serum response to Ca in rats that were ovariectomized and treated with a nano-calcium phosphate diet; additionally, the relationship between the diet and both the bone morphometry characteristics and Ca status in the body was examined. Materials and Methods: Female rats ( Rattus norvegicus ) aged 12 weeks were ovariectomized or acted as a control (non-ovariectomized rats). Euthanasia was carried out on 13-week-old control rats and ovariectomized (OVX) rats at the ages of 15, 17, 19 and 21 weeks. The 21-week-old OVX rats were divided into 3 groups and were given a nano-calcium phosphate diet containing a nano-Ca content of 0.10% (diet A), 0.40% (diet B) or 0.70% (diet C). At the ages of 27, 29, 31, 33 and 40 weeks, euthanasia was carried out for the collection of the serum, femur and tibia. The serum mineral levels [calcium (Ca), phosphorus (P) and magnesium (Mg)], morphometric characteristics (mass, mass density, length and diameter) of the long bones and Ca status in the body were analysed. Results: The results showed that in the ovariectomized rats, serum Ca and P levels decreased at week 7, while the Mg levels fluctuated. Treatment with the 0.40% nano-Ca diet could increase serum Ca levels from the 6th week of diet administration (age 27 weeks). The overall femoral morphometry and tibia characteristics, in addition to the mass density data, showed values that increased with age. The highest Ca absorption was shown by the OVX rats that consumed the 0.40% nano-Ca diet. The difference between the consumed and absorbed amounts of Ca was shown by the Ca content in the faeces, which averaged 68.07% for calcium intake. Conclusion: The female Rattus norvegicus white rats exhibited osteoporosis based on serum mineral status seven weeks post-ovariectomy. The effects of the nano-calcium phosphate diet were first observed in the sixth week of diet administration.
