Localization of NADPH-diaphorase activity in the dental pulp, periodontium and alveolar bone of the rat.

In this study we examined the presence and localization of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the dental pulp, periodontal tissues and alveolar bone of the rat. The presence of NADPH-d activity was also examined in cat pulp. The rat histochemical analysis revealed the presence of prominent NADPH-d activity both in cells of the sub-odontoblastic cell layer and in the odontoblasts, in the root as well as in the coronal pulp regions. In the pulpal horns, odontoblasts often had long processes with a high level of labelling indicating NADPH-d activity extending through the predentin and dentin. Moreover, endothelial cells of pulpal blood vessels were positive for NADPH-d in both species. However, no clearcut examples were found of pulpal nerve fibres positive for NADPH-d in the rat or cat and denervation performed in rats did not alter the enzyme staining patterns. In the periodontal tissue, NADPH-d activity was localized to cells on the alveolar bone surface of the periodontal ligament and, in addition, alveolar bone marrow crypts were filled with intensely labelled cells. In the gingival papillae, NADPH-d activity was observed in the basal cell layer of the epithelium. Endothelial cells of periodontal and gingival blood vessels showing positive staining for NADPH-d were occasionally noted.