Value of hydroxyproline measurements in the assessment of late radiation enteropathy

In female Wistar rats roentgen irradiation of a 10 cm long temporarily exteriorized mid small intestinal segment was performed. Hydroxyproline, proline, aspartic acid and threonine were measured in intestinal samples 2 to 44 weeks after single or fractionated irradiation, and compared with a histopathologic radiation injury score in order to determine their value as assays of late radiation enteropathy. Two to 4 weeks after irradiation there was good correlation between the histopathologic injury score and the content of hydroxyproline. During the late observation period, there was no difference in hydroxyproline concentration between irradiated and sham-irradiated animals. There was no difference in hydroxyproline concentration in samples from the 1, 2 or 3 fractions groups, although the relative amount of non-collagen protein seemed to increase with fractionation. Determination of the hydroxyproline concentration may be used as an assay of early radiation injury, but it seems to be less suitable for late radiation enteropathy assessment.