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Deoxypyridinoline in the Urine of Rats with Unloaded HindlimbsThe urinary excretion of deoxypyridinoline (U-Dpd), a nonreducible collagen crosslink in bone released by osteoclastic activity, is thought to be an accurate marker of bone resorption. The role of increased resorption in the osteopenia of a space flight model which unloads the hindlimbs by suspending the tail is controversial. To assess skeletal resorption in the model we measured U-Dpd (Pyrilinks-D, Metro Biosystems, Inc.) in serial 24 hour urine specimens collected from 250 a (Y) and 450 a (M) male rats with unloaded hindlimbs for four weeks. Both groups of rats were fed AIN76 diets with calcium restricted to 0.2% in Y and to 0.1 % in M. Blood was obtained after 28 days for parathyroid hormone (PTH), 1,25-dihydroxyvitamin D (1,25-D) and alkaline phosphatase (Alkptase). Basal U-Dpd was higher and more variable in Y than M (475+/-200 vs 67+/-9, nM/mM creatinine, p<.001). Repeated measures ANOVA in Y revealed decreases in U-Dpd, 36% in control (C) and 24% in unloaded (S) rats (p<.005). There was a nadir in YS on the 14th day not observed in YC (p<.05). U-Dpd in MC showed no change, but increased in MS by the 14th day and remained elevated. At the end of the experiment, body weights in both Y and M were less in S than C (337+/-16 vs 306+/-12g and 485+/-10 vs 461+/-6g, p=.002). Bill was inversely related to U-Dpd only in M (r=0.699, p=.024). PTH, similar in C and S in Y (52+/-15 vs 42+/-7pg/ml, NS) and M (68+/-13 vs 61+/-12, NS), was unrelated to U-Dpd. 1,25-D tended toward higher values in YC than YS (197+/-103 vs 119+/-30, NS) and correlated with U-Dpd (0.773, p=.015). Alkptase, 1.3 times higher in Y than M, was similar in C and S at the end of unloading. These findings indicate that bone resorption, as reflected by U-Dpd, is suppressed in young and stimulated in mature rats exposed to a space flight model. U-Dpd reflects reduced growth from the diet change in young control and experimental rats and loss of Bill in mature animals exposed to the space flight model, 2 situations with opposite effects on bone resorption.
Document ID
20020042883
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Arnaud, Sara B.
(NASA Ames Research Center Moffett Field, CA United States)
Navidi, M.
(NASA Ames Research Center Moffett Field, CA United States)
Wren, J.
(NASA Ames Research Center Moffett Field, CA United States)
Holton, Emily M.
Date Acquired
August 20, 2013
Publication Date
January 1, 1997
Subject Category
Life Sciences (General)
Meeting Information
Meeting: 18th Annual Meeting of the American Society for Bone and Mineral Research
Location: Cincinnatti, OH
Country: United States
Start Date: September 10, 1997
End Date: September 14, 1997
Funding Number(s)
PROJECT: RTOP 199-26-12-02
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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