Immunohistochemical study of chymopapain injected into the rabbit intervertebral disc using anti-chymopapain antibody.

This study was undertaken to investigate the morphological action of chymopapain (CP) in intervertebral discs. Of 20 mature Japanese white rabbits, 19 lumbar intervertebral discs were used for electron microscopic examination, and 36 discs, for immunohistochemical examination. Discs from 3 hours to 8 weeks after injection were observed by light and electron microscopy using anti-CP rabbit antibody labeled with horseradish peroxidase. Using Kagami's DMF-dehydration, two types of fine fibers were observed in the extracellular matrix of normal nucleus pulposus, in addition to collagen fiber. After injection of CP, the thinner fibers disappeared, while the thicker fibers remained. The injected CP spread from the nucleus pulposus to the annulus fibrosus within several hours and remained as long as 4 weeks. By immunoelectron microscopy, positive granules were divided into Type 1 (lacking relationship to collagen fibers) and Type 2 (adhering to or surrounding collagen fibers). The thinner fibers appear to be proteoglycan monomer and are the target for CP.