Helium-neon laser irradiation inhibits the growth of kidney epithelial cells in culture.

We have investigated the in vitro action of helium-neon (He-Ne) laser light on the cell cycle and the growth of rat kidney epithelial cell cultures. Dose-response studies showed that repeated He-Ne irradiation (dose rate 40 mW/cm2) once a day in a dose range between 11.9 and 142 J/cm2 significantly inhibited cell growth, while daily irradiation with 4.7 J/cm2 had no effect. Microscopic examination of nuclear spreads revealed an increased number of cells in mitosis after a single irradiation with 142 J/cm2. These results support previous observations suggesting that laser light of low thermal energy interferes with cell cycling and may inhibit cell growth when irradiation is performed at doses of 11.9 J/cm2 or more.