Levels of human tissue kallikrein in the vitreous fluid of patients with severe proliferative diabetic retinopathy

The aim of this study was to determine the levels of human tissue kallikrein in the vitreous fluid of patients with severe proliferative diabetic retinopathy (PDR). Tissue kallikrein levels were measured using a specific ELISA (range: 0.4-25 ng/ml) in 7 vitreous fluids from eyes with severe PDR. Seven vitreous samples from eyes which underwent vitrectomy because of rhegmatogenous retinal detachment served as non-PDR controls. Enzymatic activity was also tested by an amidolytic assay using a chromogenic substrate. In the PDR patients, vitreous tissue kallikrein was <0.4 ng/ml (5 eyes) or very low (0.52 and 0.58 ng/ml). Vitreous tissue kallikrein was <0.4 ng/ml in all non-PDR controls. These results were confirmed by the amidolytic test. Results suggest that vitreous tissue kallikrein probably plays either a secondary or no role in the pathogenesis of PDR.