Increased hydrolase activities in the human trabecular meshwork of glaucomatous eyes

Alterations in the metabolic functions of trabecular meshwork (TM) cells are thought to be involved in the pathogenesis of primary open-angle glaucoma (POAG). In an investigation of this possibility, 30 trabeculectomy specimens from patients with POAG were examined histochemically for 11 lysosomal and membrane-bound enzymes. The patients ranged from 48 to 87 years in age. The degree of enzyme staining was compared with that of 15 age-matched controls obtained from an eye bank at less than 24 h after death. There was no history of eye disease in the controls. The enzymes examined were: dipeptidylpeptidases II and IV (DPPII and IV); beta-glucuronidase (beta-GLUC); acid-beta-galactosidase (s beta-GAL); N-acetyl-beta-D-glucosaminidase (NAG); nonspecific esterase (UE); acid phosphatase (SP); alkaline phosphatase (ALP); gamma-glutamyltransferase (GGT); and aminopeptidase A and M (APA and APM). Evaluation of the specimens was performed by two observers and by computer-aided optic densitometry. Results showed increased staining of SP, UE, GGT and APM in the pathological specimens as compared with the controls. SP and UE indicate phagocytic activity, APM is involved in collagen turnover and GGT participates in both drug detoxification and the breakdown of glutathione in the gamma-glutamyl cycle. Our observations show different hydrolase activities in the TM cells of human glaucomatous eyes as compared with normal values, suggesting that such metabolic differences may be related to the pathogenesis of POAG.