Radioprotection by pretreatment with deuterated water: cytokinetic changes in the small intestine of the mouse.
All mice partially deuterated by ingestion of 29% heavy water for 12 days survived whole body gamma irradiation (8.5 Gy) from a 60Co source, whereas 42% of nondeuterated control animals died from bone marrow failure. The incorporation of 3HTdR into enterocytic DNA, as measured by autoradiography and liquid scintillation spectrometry, was used to assess the proliferative activity of small intestinal epithelium. The sequence and the magnitude of changes in tritium activity were in good agreement. Deuteration alone resulted in a reduced proliferative activity of small intestinal crypt epithelium, particularly in the basal cell positions and the first positions of the proliferation compartment. The number of positions occupied by the proliferative compartment and the crypt length were, however, barely affected by deuteration. The radiation-induced depression of DNA synthesis in the proliferative compartment was of similar magnitude in both groups. Crypt epithelium in deuterated mice, however, displayed signs of an accelerated and/or enhanced regeneration. The cytokinetic changes in deuterated animals are consistent with a protective effect for clonogenic intestinal epithelium at the time of irradiation.