IDENTIFICATION OF LEUKOCYTES IN HEALTHY RAT GINGIVAE BY ENDOGENOUS PEROXIDASE

Using the endogenous peroxidase reaction with the diaminobenzidine, I was possible to identify various types of leukocyte populations in the intercellular spaces of the junctional epithelium (JE) and adjacent connective tissue of healthy rat gingivae. Namely, neutrophils predominated, but monocytes and lymphocytes were few and eosinophils were very rare. No basophils were observed. Each leukocyte was identified by the number and shape of the peroxidase-positive and -negative granules at the electron microscopic level. Peroxidase was localized only in the azurophil granules of mature neutrophils and monocytes. The mature eosinophils also contained peroxidase only in the granules, which consisted of a peroxidase-positive matrix and a peroxidasenegative single discoid core in an equatorial position. No organellae of lymphocytes showed peroxidase-positive activity. In the inhibitory experiments for peroxidase of the identified leukocytes, 0.1 and 1M KCN inhibited the peroxidase moderately and almost completely, but 0.01M KCN and 0.01, 0.1 and 1M 3-amino-1, 2, 4-triazole (AMT) had no inhibitory effect. The endogenous peroxidase in the granules of the leukocytes, mainly neutrophils, was sensitive to KCN but insensitive to AMT. Although I found no evidence of a direct effect of the peroxidase on foreign stimuli, my findings suggest that the various leukocytes always patrol the JE and adjacent connective tissue of the healthy rat gingivae to protect against foreign stimuli.