TIME DEPENDENCY IN THE REGENERATIVE RESPONSE TO INJURY OF THE RAT CORNEAL EPITHELIUM

In the present study a central corneal epithelial defect (diameter 3.5 mm) was made in both eyes at 12:00 h in one group of rats and at 24:0 0 h in another group to see if the regenerative proliferation is influ enced by circadian rhythms. The labeling index and the mitotic rate we re registered at 4-h intervals in the perilimbal conjunctiva, the limb al area, and different parts of the cornea from the following morning until noon the day after that. The most pronounced regenerative prolif eration was seen in the midperipheral and peripheral cornea. The regen erative response occurred in both groups 24-28 h after the injury, but was highly influenced by the normal circadian rhythms, especially wit h regard to the mitotic rate. The results support the theory that even regeneration is influenced by a circadian proliferative factor.