Water, fixed charge density, protein contents, and lysine incorporation into protein in chymopapain-digested intervertebral disc of rabbit.

Chymopapain (Discase) was injected at a dose of 0.125 nanokatal unit into the intervertebral discs of rabbits, and sequential changes in the metabolism of water, proteoglycan, collagen, and noncollagenous protein were investigated separately in the nucleus pulposus, anterior, and posterior anulus fibrosus. One week after chymopapain injection, the water and proteoglycan content was lower in all of the fractionated tissues of the anterior and posterior anulus and nucleus pulposus of the discs than in the control discs. In the anterior and posterior anulus, the proteoglycan content recovered after 12 weeks, but there was no recovery in the nucleus pulposus. The collagen content continued to increase up to the 12th week in the nucleus pulposus, while the noncollagenous protein content decreased in all tissue fractions after 1 week. In the anterior and posterior anulus, the content of noncollagenous protein recovered after 3 to 6 weeks, but there was no recovery in the nucleus pulposus. The lysine incorporation in collagen and noncollagenous protein was inhibited in all tissue fractions after 12 weeks, suggesting a decrease in synthetic activity. The intradiscal pressure calculated from proteoglycan hydration at 1 to 6 weeks after chymopapain injection showed a marked decrease to 0.8 to 0.9 atm, but it recovered to 1.6 atm after 12 weeks.