FLUORESCEIN LEAKAGE TEST - A USEFUL TOOL IN OCULAR SAFETY ASSESSMENT

The fluorescein leakage test (FLT) provides information on the effects of xenobiotics on the impermeability (gate function) of epithelial ce ll monolayers, and their recovery after exposure. The aim of this stud y was to assess the validity of this test in the ocular safety assessm ent of surfactant-based products with various irritant potencies. Madi n-Darby canine kidney cells were grown to confluency on microporous me mbranes and exposed for 15 min to increasing concentrations of test su bstances. Damage was evaluated by measuring the amount of Na-fluoresce in that passed through the monolayer in 30 min, starting just after ex posure. Recovery was assessed 4, 24, 48 and 72 hr later. For each samp le and each time point, the amounts of test substance that produced 10 % and 20% leakage (FL10 and FL20) compared with a cell-free control we re calculated. For the 43 samples, FL20 values ranged from 0.65 to 100 0 mg/ml. These values increased or decreased with time according to th e substance. In particular, cell monolayers showed very different reco veries after exposure to anionic and cationic substances with similar initial FL20 values. These in vitro data correlated well with historic al Draize in vivo test data (Spearman's rho > 0.90). The FLT is theref ore useful as a complement to other in vitro methods for the ocular sa fety evaluation of cosmetics. (C) 1997 Elsevier Science Ltd.