Sensitization of hypoxic normal tissue.

The radiosensitization by misonidazole of three normal tissues in the unanaeshtetized mouse (femoral marrow, intestinal crypts and the target tissue for tail necrosis) has been studied. At 1 mg/g body weight, no sensitization was observed for the former two tissues, and no cytotoxicity for marrow was demonstrated. Sensitization of fully anoxic marrow or tail shown, by a factor of 1.8--1.9, in comparison with normal tails (factor 1.5). Clamping experiments revealed the homogenous nature of the natural hypoxia in the tissue responsible for tail necrosis, and an effective increase in the oxygenation was seen at Day 7 after a large priming dose.