Radioprotective action of haematoporphyrin on X-irradiated in trypsin.

Dose-response curves were obtained for trypsin X-irradiated in aqueous solution (4.6 x 10(-6)M), alone or after incubation with haematoporphyrin (Hp). When trypsin was irradiated alone (exposure doses ranging from 10 to 25 kR) the exponential dose-response curve showed a D37 equal to 17200 R. When trypsin was incubated with Hp before irradiation a D37 equal to 61900 R was obtained, with a dose reduction factor of 3.6. Therefore in our experimental conditions Hp shows a highly significant radioprotective action.