Abstract: AIM: To investigate timed changes of bone histomorphometry parameters in normal rats of different months and to provide a control prove for research of drugs of antiosteoporosis.METHODS: Thirty-two female rats at aged 4.5 months were divided by their weight (256.3±25.3 g).Tetracycline derivates and calcein were subcutaneous injected to each rat on two separate occasions where labeled the sites of bone formation.All rats were sacrificed at 0, 30, 75 and 140 days.The undecalcified longitudinal proximal tibial metaphyseal sections were cut and stained for quantitative bone histomorphometriy.RESULTS: The cancellous bone mass increased slowly and then decreased, but there were no significant differences between 4.5 and 10 months.Bone mass kept relatively stable.Both bone for mation and bone resorption increased first and then decreased, but there was a significant difference between 4.5 and 10 months, and bone turnover kept stable.CONCLUSION: The body weight and the bone mass parameters keep relatively stable in SD rats during the 4.5 to 10 months, and these rats can be selected as the models for the study of the drugs of antiosteoporosis.

Key words: normal rats, bone mass, different months, bone histomorphometry, bone resorption, bone formation