Chemiluminescent assay of alkaline phosphatase in human gingival crevicular fluid: Investigations with an experimental gingivitis model and studies on the source of the enzyme within crevicular fluid

The purpose of this study was to investigate how levels of gingival crevicular fluid (GCF) alkaline phosphatase (ALP) changes in relation to levels of plaque and gingival inflammation in 20 adults during a 21 day period of experimental gingivitis. The source of ALP within GCF was also investigated using a repeat sampling protocol; by determining enzyme levels derived from 30 putative periodontal pathogenic and non-pathogenic species; and by examining inhibition profiles from a variety of host and bacterial ALP isoenzymes. Total 30-s GCF ALP levels increased significantly (p<0.002) during experimental gingivitis and preceded an increase in gingival index (GI) by approximately 7 days. Enzyme levels correlated with GCF volume (R = 0.7; p<0.0001), but repeat sampling indicated that entry of ALP into the gingival crevice was independent of the rates of fluid flow. Only 5 of the bacterial species investigated produced clearly detectable levels of ALP in culture supernatants, there were P. gingivalis (381), P. intermedia (581), P. nigrescens (8944), Dentin P. gingivalis (TW 471: clinical isolate) and C. ochracea (25). Levamisole inhibition and studies on suspensions of washed plaque demonstrated that host-derived ALP contributed to >80% of the enzyme in GCF. We conclude that elevated 30-s GCF ALP levels measured using the chemiluminescent assay reported, are detected before increase in gingival indices and appear to be a better marker of gingival inflammation than ALP concentrations. The Major source of ALP within GCF is host derived and in early inflammatory disease is likely to be polymophonuclear leukocyte origin.