Comparative histochemical and biochemical studies on
acid beta-galactosidase activity in the rabbit eye after various experimental
injuries were performed using the same sensitive
fluorogenic substrate beta-galactoside-4-trifluoromethylumbelliferyl (HFC). The aim of the study was to examine whether the severity of
corneal damage corresponds with the level of the
enzyme activity in the tear fluid. As until recently the substrate beta-galactoside-4-HFC had not been used for the histochemical detection of
acid beta-galactosidase in the cornea, results obtained with this substrate in a fluorescent method were compared in parallel cryostat sections with results obtained using the substrate 5-bromo-4-chloro-3-indoxyl
beta-galactoside in the indigogenic method (previously shown to be very sensitive for the detection of
acid beta-galactosidase activity in the cornea). Both methods revealed similar localization and changes in
enzyme activity; using beta-galactoside-4-HFC an acceptable cellular localization was achieved. For the measurement of
acid beta-galactosidase activity in the tear fluid a semiquantitative biochemical method was elaborated using filter paper punches with the substrate (beta-galactoside-4-HFC) soaked with tears and incubated at 37 degrees C. The time of the first appearance of a greenish-yellow fluorescence (
enzyme positivity) was recorded by UV lamp and compared with the appearance of fluorescence in calibrated punches containing known
acid beta-galactosidase activities. The results show that beta-galactoside-4-HFC is useful for the biochemical assessment of
acid beta-galactosidase activity in the tear fluid. Comparing histochemical and biochemical results, it can be concluded that increased enzymatic activity in tears parallels the severity of
corneal damage. Further studies are necessary to evaluate whether the detection of
acid beta-galactosidase activity in tears might be useful for diagnostic purposes in humans.