IN-SITU DETERMINATION OF DIFFERENT DEHYDROGENASE-ACTIVITY PROFILES INTHE LININGS OF ODONTOGENIC KERATOCYSTS AND RADICULAR CYSTS

The levels of succinate, lactate, glutamate, glycerophosphate and gluc ose-6-phosphate dehydrogenases within the linings of keratinizing and non-keratinizing odontogenic cysts were investigated using static end- point acid continuously monitored Nitroblue Tetrazolium-based histoche mical methods. The use of TV image analysis for quantification of form azan final reaction products was validated by demonstrating significan t relationships between the integrated absorbance at 585 nm and the am ount of formazan in, and thickness of, gelatin films containing reduce d tetrazolium salt (r = 1.0, p<0.001). Absorbance readings of stained sections gave mean coefficients of variation of 1.8 +/- 0.9% between d ay of measurement, and of 5.65 +/- 1.32% between serial sections. End- point assays indicated that the linings of odontogenic keratocysts con tained higher levels of glucose-6-phosphate dehydrogenases (p<0.0002) and lower levels of lactate dehydrogenase (p<0.002) than those of radi cular cysts. Succinate, glutamate and glycerophosphate dehydrogenase a ctivities were similar in both cyst types. Results from continuously m onitored assays, performed for glucose-6-phosphate and succinate dehyd rogenases, demonstrated linear reaction rates over the first 2.75 min of reaction. The calculated enzyme activities from continuous assays w ere between 1.49 and 3.49 times higher than those determined from end- point assays and confirmed that levels of glucose-6-phosphate dehydrog enase were significantly higher in the linings of odontogenic keratocy sts than those of radicular cysts (p<0.004). By contrast, succinate de hydrogenase activity was significantly higher in radicular cyst lining s (p<0.03). These results highlight the benefits of an approach to in situ determination of enzyme activity using image analysis and continu ous monitoring methodologies. Overall, the high level of glucose-6-pho sphate dehydrogenase found in keratocyst Linings is consistent with th eir clinical behaviour and higher level of proliferation and synthetic activity whereas the level of lactate dehydrogenase in radicular cyst s probably reflects the presence of local tissue damage within these i nflammatory lesions.