Proteolytic activity of developing dentine of rat tooth germs revealed by the gelatin-film substrate technique.

The ability of tooth germs to breakdown gelatin was investigated by incubating unfixed cryostat sections of 3-8 day rat molar tooth germs on processed photographic plates. Breakdown of gelatin occurred exclusively in regions which were overlain by developing dentine and bone, suggesting that these tissues contain proteolytic enzymes. As the proteolytic activity occurred at a pH closer to that of the extracellular fluid, i.e. closer to neutrality, it is proposed that neutral proteases, presumably released by odontoblasts, breakdown components of the organic matrix during dentinogenesis. The products of breakdown may, in turn, be taken up by odontoblasts to be further degraded in their extensive lysosomal-vacuolar system. Breakdown and resorption of matrix components may reflect the normal turnover of matrix materials, or may be a mechanism concerned with the regulation of either the amount of materials present in the matrix or its chemical composition during dentinogenesis.