Tear malate dehydrogenase, lactate dehydrogenase and their isoenzymes in normal Chinese subjects and patients of ocular surface disorders

Abstract

Purpose: To determine levels of malate dehydrogenase (MDH), lactate dehydrogenase (LDH) and their isoenzymes in tears of normal Chinese subjects and patients with ocular surface disorders.

Methods: The age range of normal subjects was 10-88, with 136 male and 128 female subjects. 123 patients suffered from ocular surface disorders. Tears were collected from lower fornix on Xinghua filter disc (0.1mm thick, 5mm in diameter). The values of tear MDH and LDH were determined by MONARCH-2000 Analyzer (U. S. A.). Their isoenzymes were separated by acetate cellulose electrophoresis and were determined by Model CDS-200 light densitometer.

Results: The normal values of tear LDH and MDH were 45.51 + 23.00-81.35 + 37.84 umol.s-1/L and 11.00 + 5.33-19.50 + 9.17 umol.s-1/L respectively, disregarding sex or eye distriction (P > 0.05). The values of tear LDH and MDH in the group aged 10-19 were significantly lower than in another groups (P < 0.05). 95% normal ranges of tear MDH aged below 19 and above 20 were 3.63-19.90 umol.s-1/L and 4.20-36.64 umol s-1/L. 95% normal ranges of tear LDH aged below 19 and above 20 were 17.69-82.93 umol.s-1/L and 21.47-150.41 umol.s-1/L. The MDH isoenzymes comprised MDHs and MDHm, the former accounting for 80.0-89.1%. The LDH isoenzymes comprised 5 varieties, of which the ratio H/M of subunit H to subunit M was 0.196 + 0.02. Levels of tear LDH,MDH and their isoenzymes in different diseases were various.

Conclusions: Tear LDH/MDH ratio reflected sensitively the metabolism of corneae and conjunctival epithelium. The changes in LDH isoenzymes were helpful to the differential diagnosis of external eye diseases, and the increase of MDHm reflected sensitively the degree of injury to the corneal epithelium.