EFFECT OF TEAR PROTEINS ON PRESERVATIVE TOXICITY TO EPITHELIAL-CELLS

Eye irritation caused by preservatives in ophthalmic formulations and cosmetics may be affected by the presence of proteins in tears. This h ypothesis was investigated by combining preservatives with proteins no rmally present in tears, that is, albumin, lysozyme, and immunoglobuli ns, and evaluating them with in vitro models of corneal cytotoxicity. A panel of nine cationic preservatives was tested that included benzal konium chloride (BAK), a preservative often present in ophthalmic prep arations. The studies utilized the vital dyes neutral red and ethidium bromide as indicators of cellular membrane damage. The MDCK epithelia l cell line and cultured rabbit corneal epithelial cells were used as ocular models. The results demonstrate that the cytotoxicity of BAK an d other preservatives was significantly reduced in the presence of tea r proteins. Therefore, the role of tear proteins should be taken into consideration when in vitro tests of eye irritation are conducted.