No abstract

The present study was performed to clarify the effects of a 4-min exposure of mitomycin C (MMC) on cell growth, the cell cycle and MMC dose incorporated into DNA, using Chang’s cultured human conjunctival cells. A low dose of MMC ranging from 0.00025 to 0.004% showed dose-dependent cytotoxicity when cell growth was active. Fifty percent cell viability was found when cells were treated with 0.001% MMC. A flow cytometer showed that 0.001% MMC inhibited the DNA synthetic phase. After 0.04% MMC was exposed to 3 ×10⁶ cells and immediately rinsed, DNA was isolated to measure the dose of MMC detected from DNA. The total amount of DNA was 7 µg from which 3 µg of MMC was detected by high performance liquid chromatography. The above results revealed that the lowest concentration of MMC which caused 50% cell viability and cell cycle inhibition was 0.001% and that MMC was rapidly incorporated into DNA.

Corneal epithelial disorders due to isopropyl unoprostone (unoprostone) eye drops, a prostaglandin F2alpha-related substance and antiglaucoma agent, have been reported since the agent became commercially available. The in vitro study was performed to clarify the mechanism of cell injury due to unoprostone. After Chang's human conjunctival cells were cultured and exposed for 2, 4 and 8 min to 0.03, 0.06, and 0.12% unoprostone and its vehicle containing 1% polysorbate 80, a cell growth assay and DNA histogram analysis using a flow cytometer and scanning electron microscopy were performed. The number of living cells was reduced, and the floating cell number increased immediately after exposure to 0.12% unoprostone for 8 min. When the cells were cultured for another 48 hr after exposure to unoprostone, the cell number was reduced dose and time dependently. Exposure for 2 min to 0.12% unoprostone showed no effect on the cell cycle. However, exposure for 2 min to 0.12% unoprostone caused alteration of the cell surface, such as reduction of microvilli and filopodia. The vehicle did not affect the cell surface or cell growth. These results suggest that clinically instilled eye drops ofunoprostone can affect cell structure, inhibit cell growth, and gradually cause corneal epithelial disorders.