A study of connective tissue metabolites in biological fluids of patients with various types of glaucoma

PURPOSE. To quantify the content of connective tissue metabolites reflecting the exchange of its main components in biological fluids in low tension glaucoma (LTG) and primary open-angle glaucoma (POAG), and to conduct a comparative analysis of the obtained data. METHODS. The studies were conducted in 33 patients with low tension glaucoma aged 51 to 80 years old (mean age 69 ± 10.4 years), 20 patients with POAG aged 53 to 80 years old (mean age 67 ± 10.1 years) and 15 clinically healthy volunteers aged 52 to 78 years old (mean age 68 ± 9.2 years). The protein components of the fibrous part of the connective tissue were analyzed for daily excretion of oxyproline in urine by the method involving para-Dimethylamin-obenzaldehyde modified by P.N. Sharaev. Serum glycosaminoglycans (GAG) were studied by analyzing carbohydrate components of connective tissue. The concentration of GAG in the blood serum was determined by the colorimetric method, using Dische's carbazole reaction. RESULTS. The amount of GAG in the blood serum of LTG patients was 3.26 ± 1.57 mmol/L, while in the control group consisting of clinically healthy volunteers — 2.92 ± 1.25 mmol/L. The differences were not statistically significant (p > 0.1). The amount of daily excretion of oxyproline in the urine of LTG patients was 17.17 ± 8.64 mmol/day, and in the group of clinically healthy individuals — 13.96 ± 5.61 mmol/day. The differences were statistically significant (p < 0.05). The amount of GAG in the blood serum of POAG patients was 3.97 ± 1.17 mmol/L. The differences in relation to LTG were statistically significant (p < 0.05). The amount of daily excretion of oxyproline in the urine of POAG patients was 32.71 ± 19.79 mmol/day. The differences were statistically significant in relation to LTG (p < 0.05). The amount of GAG and oxyproline in biological fluids tends to increase with the advancement of LTG and POAG. CONCLUSION. Destruction processes in the connective tissue do occur in LTG, but are less pronounced in comparison to POAG and more pronounced in comparison to healthy individuals. The indicator that most clearly reflects the activity of destructive processes in the connective tissue is the daily excretion of oxyproline in urine.