Are skeletally mature female rats a suitable model to study osteoporosis?

objective: to analyze if female wistar rats at 56 weeks of age are a suitable model to study osteoporosis. materials and methods: female rats with 6 and 36 weeks of age (n = 8 per group) were kept over a 20-week period and fed a diet for mature rodents complete in terms of ca, phosphorous, and vitamin d. excised femurs were measured for bone mass using dual-energy x-ray absorptiometry, morphometry, and biomechanical properties. the following serum mar-kers of bone metabolism were analyzed: parathyroid hormone (pth), osteocalcin (oc), osteoprotegerin (opg), receptor activator of nuclear factor κappa b ligand (rankl), c-terminal peptides of type i collagen (ctx-i), total calcium, and alkaline phosphatase (alp) activity. results: rats at 56 weeks of age showed important bone metabolism differences when compared with the younger group, such as, highest diaphysis energy to failure, lowest levels of oc, ctx-i, and alp, and elevated pth, even with adequate dietary ca. conclusion: rats at 26-week-old rats may be too young to study age-related bone loss, whereas the 56-week-old rats may be good models to represent the early stages of age-related changes in bone metabolism.