Smith S M, Nillen J L, Leblanc A, Lipton A, Demers L M, Lane H W, Leach C S
Life Sciences Research Laboratories, National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas 77058, USA.
J Clin Endocrinol Metab. 1998 Oct;83(10):3584-91. doi: 10.1210/jcem.83.10.5169.
Extended exposure to weightlessness results in bone loss. However, little information exists as to the precise nature or time course of this bone loss. Bone resorption results in the release of collagen breakdown products, including N-telopeptide and the pyridinium (PYD) cross-links, pyridinoline and deoxypyridinoline. Urinary pyridinoline and deoxypyridinoline are known to increase during bed rest. We assessed excretion of PYD cross-links and N-telopeptide before, during, and after long (28-day, 59-day, and 84-day) Skylab missions, as well as during short (14-day) and long (119-day) bed-rest studies. During space flight, the urinary cross-link excretion level was twice those observed before flight. Urinary excretion levels of the collagen breakdown products were also 40-50% higher, during short and long bed rest, than before. These results clearly show that the changes in bone metabolism associated with space flight involve increased resorption. The rate of response (i.e. within days to weeks) suggests that alterations in bone metabolism are an early effect of weightlessness. These studies are important for a better understanding of bone metabolism in space crews and in those who are bedridden.
长期暴露在失重环境中会导致骨质流失。然而，关于这种骨质流失的确切性质或时间进程的信息却很少。骨吸收会导致胶原蛋白分解产物的释放，包括N-端肽和吡啶鎓（PYD）交联物、吡啶啉和脱氧吡啶啉。已知卧床休息期间尿中吡啶啉和脱氧吡啶啉会增加。我们评估了在长时间（28天、59天和84天）的天空实验室任务之前、期间和之后，以及在短期（14天）和长期（119天）卧床休息研究期间PYD交联物和N-端肽的排泄情况。在太空飞行期间，尿中交联物排泄水平是飞行前观察到的两倍。在短期和长期卧床休息期间，胶原蛋白分解产物的尿排泄水平也比之前高40 - 50%。这些结果清楚地表明，与太空飞行相关的骨代谢变化涉及吸收增加。反应速度（即几天到几周内）表明骨代谢改变是失重的早期影响。这些研究对于更好地理解太空船员和卧床者的骨代谢非常重要。
