To clarify a role of neutrophil lysosomal proteinases in periodontal tissue breakdown, their nature in neutrophils and their levels in gingival crevicular fluid (GCF) of periodontitis patients were investigated. When the distribution of these proteinases in the neutrophil granular subfractions was analyzed, cathepsins B and H were made soluble by hypotonic shock. Cathepsins L and G were made soluble after washing the membrane with 1M NaCI. On the other hand, about 30% of hemoglobin (Hb) -hydrolase (s) was tightly associated with the membrane after both treatments. Immunochemical analyses revealed that about 35% of the total Hb-hydrolase activity was attributed to cathepsin D, which was found in the content fraction, and the rest were due to pepstatin-insensitive serine proteinase (s) . Differing from rat neutrophils, human neutrophils do not contain cathepsin E. The ratio of cathepsin D to the serine proteinase (s) in neutrophils was not changed in GCF from periodontitis patients and these enzymes were associated with development of the disease.
The quantity of cathepsin B in GCF of periodontitis patients determined by enzyme immunoassay was closely correlated with that by activity measurement, indicating that cathepsin B increases with the increase of severity of the disease and that its level in GCF can be inferred by activity measurement.
