Quantitative evaluation of the effectiveness of taurine in protecting the ocular surface against oxidant

Quantitative evaluation of the effectiveness of taurine against ocular surface damage caused by hypochlorous acid (HOCl) was investigated using albino rabbits. The activity of lactate dehydrogenase (LDH) released from ocular tissues into meniscus tears at eye irritation was used as an index of ocular surface damage. Instead of collecting meniscus tears directly with a glass micropipette, a new sampling method, where 150 microliters of saline was instilled into the cul-de-sac of rabbit eyes and collected all of the diluted tears within 10 s, was developed. The LDH activity after serial instillations of HOCl increased dose-dependently with increasing HOCl concentration. After serial instillation of taurine, HOCl was instilled in the same way. Pre-application of taurine effectively suppressed (p < 0.01, n = 11) the HOCl-induced LDH release as compared to saline, suggesting that the residual taurine in ocular surface tissues was still effective in protecting the tissues against HOCl by scavenging HOCl. LDH activity at 30 in after post-application of taurine was significantly lower (p < 0.01, n = 10) than that in the case of saline. This result indicates that taurine is effective in protecting the ocular surface after it has been attacked by HOCl. LDH activity in meniscus tears became a good index of quantitatively estimating ocular surface damage due to HOCl by devising the new sampling method. By using this method, we were able to prove objectively and quantitatively that taurine is effective in protecting the ocular surface against HOCl. It was suggested that taurine is clinically useful in the treatment of ocular surface damage caused by oxidants, such as HOCl.