The effects of space flight on the composition of the intervertebral disc.

The lumbar annuli of rats flown on a COSMOS space flight were compared with those of three control groups and a ground antigravity tail suspension model. The wet and dry weights of the space flight annuli were significantly smaller than the three control groups. In addition, the collagen-to-proteoglycan ratio was significantly greater in the flight group due to a proportional increase in collagen and a decrease in proteoglycan. Finally, it appears microgravity may have altered the nature of the proteoglycan population as more proteoglycans leached from the annuli of flight animals than control animals when immersed in water.