A histochemical study of arylaminopeptidases and alkaline phosphatases in sound and carious human teeth

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Abstract
Fresh, undecalcified sections (of 6—20 μm) from intact or carious human teeth as well as teeth with different types of pulpal inflammation were cut in a heavy duty microtome at —20° C. Scotch tape was used to stabilize the teeth during sectioning. The localization of arylaminopeptidases (EC 3.4.1.) and alkaline phosphatase (EC 3.1.3.1.) was demonstrated histochemically using an azo dye principle. The teeth were also examined by microradiography. No arylaminopeptidase activity was normally observed in intact teeth by the histochemical method. In carious teeth, however, this enzyme activity could be localized in the dentinal tubules of the carious lesion, whereas sound dentin, predentin and pulp did not reveal any activity. The inflamed part of the pulp was observed to reveal marked arylaminopeptidase activity. Alkaline phosphatase was observed to be localized mainly in the predentin layer and in the subodontoblastic layer of the pulp and additionally in the cementum and in the remaining parts of the periodontal membrane in intact and carious teeth. This activity disappeared from the odontoblast and subodontoblast zones at exposure due to caries and was observed to precede the inflamed part of the pulp with partial pulpal inflammations. The borderline between sound and carious dentin was detected by microradiography. On the basis of their distribution arylaminopeptidases were considered as «attacking enzymes», whereas alkaline phosphatases were considered as «response enzymes» in the carious process and pulpal inflammations.