The Features of Development of Osteoporosis in SenescenceAccelerated OXYS Rats

Abstract—Osteoporosis in OXYS rats is one of the signs of their accelerated aging. Previously, we regarded it as senile. However, in this study osteoporotic changes in the metabolism of OXYS rats have been revealed in the early postnatal period. They may lead to the development of osteoporosis in the future and may underlie the formation of a reduced peak bone mass. One hundred and eighty OXYS and Wistar (the control group) rats aged from 10 days to 24 months have been used in this study. No differences in the bone mineral density (BMD) in OXYS and Wistar rats at the age of 10 days and 3 months were observed. On the tenth day, the activity of alkaline phosphatase (ALP), a marker of osteoblast activity, was maximum in both OXYS and Wistar rats. However, OXYS rats showed an activity 40% higher than Wistar rats. With age, ALP activity decreased and after 3 months it was half in OXYS rats than it was in Wistar rats. The peak bone mass in Wistar rats is formed by the age of 12 months, and in OXYS rats it is formed already by 6 months, but it does not reach the level of the Wistar rats. The content of calcium (Ca) in the blood and bone tissue changes similarly. In OXYS rats after 6 months, it decreased simultaneously with Ca. The bone phosphorus (P) was the same in both groups, and the bone strontium (Sr) was lower in OXYS rats aged 6 and 12 months. Nevertheless, these changes in the mineral composition of bone in OXYS rats did not affect their mechanical strength. The absolute strength of the long bones in OXYS rats aged 12 months was lower than that of Wistar rats. However, this is due to a decrease by 1.7 times in crosssectional area and the standardization per area unit neutralizes the difference. We found that OXYS rats demonstrate a genetically determined hypoplasia of the bone tissue, which may be associated with the development of idiopathic osteoporosis.