Purpose. To determine the effect of mitomycin-C on confluent and non-c
onfluent human retinal pigment epithelium (RPE) in tissue culture. Met
hods. The effect of mitomycin-C on confluent RPE was determined by tre
ating first passage confluent cells with 0.01, 0.1, 1, 10, 100 or 1000
micromolar (mu M) mitomycin-C for 1, 3. or 7 days. The cell viablilit
y after treatment was determined by using an esterase stain. The effec
t of mitomycin-C on proliferating RPE was determined by incubating non
-confluent cells with the above concentrations of mitomycin-C for 20 m
in, 1 hour or 24 hours. Results. Mitomycin-C can be toxic to a conflue
nt RPE monolayer, and the LD50 is 421, 28.8 or 0.0632 mu M when cells
are continually exposed to mitomycin-C for 1, 3 or 7 days, respectivel
y. Exposure to mitomycin-C at concentrations greater than or equal to
10 mu M for 20-60 min significantly inhibits proliferation of non-conf
luent RPE. A 24 hour exposure of RPE to 1 mu M mitomycin-C markedly in
hibits proliferation of non-confluent RPE with minimal toxicity to con
fluent RPE. Conclusions. Since exposure of human RPE to mitomycin-C fo
r 24 hours can inhibit cell proliferation at concentrations which are
well-tolerated by confluent RPE, mitomycin-C may be a suitable agent f
or inhibiting RPE proliferation in vivo.