Journal of Applied Physiology, Vol 73, Issue 2 26S-32S, Copyright © 1992 by American Physiological Society
Effects of microgravity on the composition of the intervertebral disk
A. Pedrini-Mille, J. A. Maynard, G. N. Durnova, A. S. Kaplansky, V. A. Pedrini, C. B. Chung and J. Fedler-Troester
Department of Orthopaedic Surgery, University of Iowa, Iowa City 52242.
The lumbar annuli of rats flown on COSMOS 2044 were compared with those of
three control groups and a tail-suspension experimental model. The wet and
dry weights of the annuli were significantly smaller (P less than 0.05) in
the flight group than in three control groups. The collagen-to-proteoglycan
ratio was significantly greater (P less than 0.001) in the flight group
than in the three control groups, but there were no detectable changes in
the relative proportions of type I and II collagen or in the number of
pyridinoline cross-links. When the annuli were immersed in water for 2 h,
more proteoglycans (P less than 0.001) leached from the annuli of flown
rats than from the tissue of control animals, suggesting abnormal or
smaller proteoglycans. Safranin-O indicated a normal spatial distribution
of the proteoglycans within the annulus. Tail suspension did not affect the
size of the annuli, but more proteoglycans (P less than 0.05) leached from
the tissue of suspended animals than from the normal annuli. The reasons
for smaller disks and the abnormal ratio between the fibrous collagenous
network and the proteoglycan gel in the flight group are unknown at this
time. It is, however, probable that these changes may affect the
biomechanical functions of the annulus, although they may be temporary and
totally reversible if injuries are avoided in the interim period.
