Effects of irradiation on marrow stromal cells with respect to committed granulocyte-macrophage progenitor cells

The effects of irradiation on the growth regulatory function of marrow stromal cells (MSC), and on the committed granulocyte-macrophage progenitor cells (GM-CFC), were investigated using a liquid culture system. CSF activity in the supernatant of irradiated MSC (0-900 rads) increased markedly with the increase of MSC irradiation dose. CSF-inhibitory activity in the supernatant of irradiated MSC (0-900 rads) also increased with the increase of MSC irradiation dose. Furthermore, the activity of exogenous CSF added to the supernatant of 900 rad-irradiated MSC was lost more slowly than that of non-irradiated MSC. These data suggest that irradiation affected CSF production, inhibitor production and consumption of CSF by MSC.