LYSOSOMAL-ENZYME AND INHIBITOR LEVELS IN THE HUMAN TRABECULAR MESHWORK

Purpose. To examine in the human trabecular meshwork lysosomal enzymes and one inhibitor of serine proteases that actively participate in th e degradation of macromolecules into low molecular weight constituents . Methods. Using an avidin-biotin-peroxidase technique, lysosomal prot eases and alpha-proteinase inhibitor were examined in the trabecular m eshwork of 23 human eyes with donor ages ranging from 2 to 90 years. T hese eyes were categorized into three age groups (less than or equal t o 20, 21 to 49, and greater than or equal to 50 years). Histochemical staining for lysosomal hydrolases was also performed on frozen section s of 20 human eyes. The staining was analyzed by an image analyzer and the levels of lysosomal proteases were further measured by biochemica l assays. Results, The trabecular meshwork from all the eyes stained i ntensely against antibodies to cathepsins B and G and alpha 1-proteina se inhibitor. The staining for elastase was weaker but evident. Image analyses revealed that the staining intensity for each protease or inh ibitor was similar in all age groups: The staining in the uveal meshwo rk appeared to be the strongest among all the trabecular meshwork regi ons. Biochemical assays of tissue extracts confirmed that the enzyme a nd inhibitor levels were comparable among the three donor age groups. Activities of two lysosomal hydrolases, acid phosphatase and acid este rase, were also found in trabecular meshwork cells of 20 eyes. No appa rent difference in enzyme activities was found with increasing age, an d variation related to region was not observed. Conclusions. This stud y demonstrated the age-independent distribution of a variety of lysoso mal enzymes and a protease inhibitor in the human trabecular meshwork. The presence of these proteins suggests a possible role in the metabo lic operation of the trabecular meshwork.