Sensitivity and Protection of Mouse Bone-marrow Cells X-irradiatedin Vitro

Abstract
The 30-day survival of mice exposed to a lethal dose (798 r) of x-rays was a function of the number of isologous bone-marrow cells injected. From this calibration curve it was possible to determine the surviving fraction in a suspension of marrow cells irradiated in vitro. The in vitro radiation-response of such suspensions could be represented by a typical exponential survival curve the linear part of which indicated a D37 of 84 r and an extra-polation number of 2·5. Cysteine, S,2-aminoethylisothiuronium chloride, and anoxia protected marrow cells irradiated in vitro and gave dose reduction factors ranging from 1·7–2·1. Noradrenaline did not protect the cells.