Irradiation with He-Ne laser increases ATP level in cells cultivated in vitro.

A monolayer of HeLa cells was irradiated with an He-Ne laser (632.8 nm, 100 J m-2, 10 s) and the amount of adenosine triphosphate (ATP) was measured by the luceferin-luciferase bioluminescent assay technique at different times (5-45 min) after irradiation. The amount of ATP in the log phase of cultured cells remained at the control level (0.79 +/- 0.09) x 10(-15) mol per cell) during the first 15 min after irradiation; it then increased sharply and, after reaching a maximum (170.8%) 20 min after irradiation, decreased slowly to the control level. The ability of monochromatic red light to induce an increase in the cellular ATP level was found to depend on the growth phase of the culture, being insignificant in the lag phase of cultured cells, increasing in the log phase of cultured cells and reaching a maximum (about 190%) in cells at the late logarithmic and early plateau phase.