GLUCOSE-DEPENDENT REGULATION OF DNA-SYNTHESIS IN BOVINE RETINAL ENDOTHELIAL-CELLS

Purpose. Clinical trials have demonstrated that the onset and progress ion of diabetic retinopathy is influenced by the glucose control of th e patient. The disease is characterised by the coexistence of impaired cell growth and excessive cell proliferation, and we wished to determ ine the effect that glucose has upon these parameters. Methods. Bovine retinal endothelial cells were exposed to a range of glucose concentr ations from 0-25 mmol/l. The level of DNA synthesis and cell number wa s then determined using pulse labelling with tritiated thymidine and a Coomassie blue dye-based assay, respectively. Results. The level of D NA synthesis declined significantly as the concentration of glucose in creased. DNA synthesis was further decreased by the presence of an inh ibitor of PI3 kinase (Wortmannin). The decline in DNA synthesis was ab rogated by the presence of a protein kinase C (PKC) inhibitor or by in cubating the cells with antibodies specific for the GLUT-1 and GLUT-3 specific isoforms of glucose transporter proteins. TGF-beta antibody s ignificantly increased the level of DNA synthesis in cells exposed to high concentrations of glucose. The changes that are observed in the l evel of DNA synthesis was not coincident with any significant changes in cell number as measured by the Coomassie blue assay. Conclusions. T his demonstrated that the decline in DNA syn thesis is dependent upon the entry of glucose into the cells and that this is mediated via a PK C dependent pathway.