EARLY CELL KINETIC EFFECTS OF A SINGLE-DOSE OF NARROW-BANDED ULTRAVIOLET-B IRRADIATION ON THE RAT CORNEAL EPITHELIUM

The right eyes of 40 rats were exposed to a single erythemogenic dose of ultraviolet B irradiation (UVB) at 297 nm. The irradiation was dire cted perpendicular to the center of the cornea. The left eyes served a s controls. The animals were randomly assigned into 10 groups. The lab eling index (LI) after pulse labeling with tritiated thymidine and the mitotic rate (MR) after Colcemid administration were registered in th e corneal epithelium at predetermined intervals up to 96 h after the i rradiation. A mathematical method was used to correlate corresponding corneal areas from the different animals. In the central cornea the LI was considerably reduced up to 36 h after the irradiation. The LI inc reased toward the peripheral cornea and reached normal values at the l imbal area. The MR was also reduced up to 36 h. However, this reductio n was over the entire epithelium. The block in cell proliferation was followed by increased proliferation.