Figure 7. The number of BrdU positive
cells in the RPE following multiple pulses at progressive times. BrdU
was given as a single pulse (50µg/kg) or as multiple pulses in 2 month
old DA rats. For comparison animals were given 4 injections at 3 h
intervals and euthanized 3 h later. Similar experiments were undertaken
at 12 h intervals, with single pulse and euthanized 12 h later compared
with 4 pulses separated by 12 h each and euthanized 12 h after the last
pulse. There was no statistically significant increase in labeled cells
following multiple injections compared with single injections. However,
when BrdU was pulsed at 24 h intervals over 5 days, there was a
significant increase in the number of RPE labeled cells compared with
labeling in any of the other groups (ANOVA, p<0.0001. Dunnett’s
Multiple Comparison Test p<0.001). Hence the RPE population is
proliferating, but with a cell cycle rate of approximately 5 days.