Histology and histochemistry of intervertebral discs of rats participated in spaceflight.

The qualitative and quantitative histological and histochemical changes in the structure and macromolecular composition of lumbar intervertebral discs of rat during a 12.5-day space flight (Cosmos 1887 biosatellite) were determined using light and polarization microscopy. Semiquantitative histochemical, topo-optical reactions were measured and evaluated by retardation values of birefringence. (a) Lateral expansion and accumulation of the notochordal cells in the nucleus pulposus was observed in contrast with the vivarium control, where the chondroid cells dominated. (b) The cartilage and plate showed a swelling, which consisted mainly of hypertrophied cells sometimes with mild extracellular mineralization. (c) In the external zone of annulus fibrosus and cartilage end plate a mild decrease of orientation of collagen fibers was found. (d) A significant increase of orientation of hyase sensible glycosaminoglycans in the internal zone of annulus fibrosus and nucleus pulposus was observed. (e) In the external and internal zones of annulus fibrosus an increase of orientation of glycoproteids was revealed. The alterations of macromolecular components of intervertebral discs, cartilage end plates, and the osteoporotic changes of the lumbar vertebral bodies producing the looser structure of vertebral column after 12.5 day space flight suggest the necessity of the common evaluation of these structures, and may explain the heavy spinal pains of astronauts.