Further observations on in vivo radioprotection of rats by selenourea.

Some chemical considerations have suggested that selenium-containing compounds should be good radioprotectors. Shimazu and Tappel reported that the selenoanalogues of cystine and methionine were effective in the radioprotection of proteins and amino acids in solution*. Earlier investigations in our labora­ tories have shown that selenourea has a radiopro­ tective effect in chemical systems 2, in rats3’ 4 and in bacteria5. In particular in rats, selenourea was able to reduce the lethality, some clinical symptoms of radiation injury and the severity of haematological syndrome (depression of white cell count and of neutrophiles in blood). This paper reports further investigations and new results on the effect of selenourea in irradiated rats. The parameters investigated were the total protein content and the protein pattern of serum and some changes in the activity of plasma enzymes like alkaline phosphatase (AP), glutamate oxalacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT). Groups of eight male Wistar rats of an average weight of 150 g were exposed to 750 R (about LD 50) total body gamma irradiation by means of a 60Co therapy apparatus with a dose rate of 30 R/ min. Selenourea, at a single dose of 1 mg/ml of physiological solution, was injected intraperitoneally to a group of rats 10 min prior to irradiation. At fixed time after the irradiation, from the animal, subjected to cardiopuncture following Nembutal anaesthesia, were taken blood samples for the bio­ chemical analysis. The serum proteins were sepa­ rated by means of paper electrophoresis technique and the enzymatic analysis were carried out with the standard methods described in the literature 6. The administration of selenourea in unirradiated rats does not cause any change in the investigated parameters. Table I shows the effect of selenourea on the radiation-induced changes in protein content and in protein pattern of rat serum. Data on the effect of cysteine, a well known radioprotective agent, are also given for comparison. The mean values are summarized together with the standard errors for the means. In the irradiated control rats the total protein values of the serum were significantly de­ creased and the concentration of albumin decreases much more than that of globulins. These modifica­ tions are in agreement with other published works 7. The modifications induced by the presence of