Cytochemical localization and distribution of a lactate utilizing enzyme system in human gingiva

Abstract

Employing nitro blue tetrazolium chloride (Nitro BT), histochemical evidence was obtained for the distribution and localization of the lactate dehydrogenase-Nitro BT-reductase (LDR) system in human gingiva. The stratum germinativum, middle stratum spinosum, lower cells of the stratum granulosum, endothelial and muscular layers of the arterioles and venules, vasa vasorum and most of the connective tissue cells exhibited high activities. Relatively lesser activity was observed in the lower stratum spinosum, upper stratum granulosum and nerve structures of the connective tissue. Formazan deposition in the presence of lactate alone was mild and is indicative of the level of available endogenous DPN and, thus, functional lactate dehydrogenase capacity of the tissue under our experimental conditions. The addition of external DPN to the lactate reaction mixtures greatly intensified formazan staining. Formazan reaction was enhanced further upon the addition of cyanide. These reactions demonstrate the total potential LDR activity. In both instances the distribution of LDR in the epithelium differed from that previously described for DPNH 2 reductase. Positive LDR reaction also was observed in desmosomes, tonofibrils, intercellular bridges, keratohyalin granules and nucleoli, confirming their probable metabolic potential. The role of the LDR system in the respiratory and glucolytic or glycolytic metabolism (aerobic and/or anaerobic) in conjunction with morphogenesis of the gingival epithelium is discussed.