A dose-surviving fraction curve for mouse colonic mucosa.

A dose-surviving fraction curve representing the response of the mouse colonic mucosa to single doses of 137Cs gamma radiation was obtained from the results of a multifraction in vivo colony assay. Construction of the curve required an estimate of the average number of clonogens initially present per colonic crypt. The estimated clonogen count (88) was determined by a statistical method based on the use of doses per fraction common to different fractionation protocols. Parameters for the LQ and TC models of cell survival were obtained by weighted least-squares fits to the data. A comparison of the survival characteristics of cells from the mouse colonic and jejunal crypts suggested that the epithelium of the colon is less radiosensitive than that of the jejunum.