[Age-related changes in bone weights and their components in rats].

Abstract

Age-related changes in the wet, dry and ash weights and components such as water, organic substance, ash, calcium and phosphorus of femur, tibia and first lumbar vertebra and serum biochemical constituents related to bone metabolism were examined in Wistar rats. A total of 60 males and 60 females were used, and every five rats of both sexes were examined at 1 and 2 months of age and then at intervals of 3 months between 3 and 30 months of age. Each bone weight increased rapidly up to 3 months of age and then gradually up to 12 months of age in females and 9 months of age in males, but thereafter decreased at 27 and 30 months of age in males. Between 1 and 6 or 9 months of age in both sexes, a decrease in water content, increases in ash, calcium and phosphorus, and almost no change in organic substance in each bone were observed. After 15 months of age in males, an increase in water content, decreases in ash content, calcium and phosphorus, and almost no changes in organic substance were observed in males. The value of serum calcium decreased up to 12 months of age but then increased after 18 months of age in both sexes. Serum phosphorus and alkaline phosphatase activity decreased up to 9 months of age in both sexes. The data obtained in this study supported the results in our previous study that the peak bone strength of the femur and peak bone volume of trabecular bone of the proximal metaphysis of the tibia were at 12 months of age in both sexes in Wistar rats.