Control of cell division in the cornea of rats. III. Mitogenic effect of isoproterenol and theophylline.

The effects of isoproterenol, theophylline and the combination of the two drugs were studied on the circadian mitotic rhythm in rat corneal epithelium. The drugs induced profound alterations in the normal circadian mitotic pattern. The alterations included an initial suppression of cell division, followed by two distinct rises above control; the first immediately following suppression, the second 12-16 hr following drug administration. The second peak of cell division occurred at the circadian trough in controls. The simultaneous administration of isoproterenol and theophylline greatly magnified the effects seen with either drug alone.