大腸菌並びにマウスのγ線照射に対する含硫アミノ酸誘導体の防護,増感効果に関する研究

Both protection and sensitization of E. coli NIHJ and C 57 BL mice against (60)Co γ-rays by sulfur-containing amino acid derivatives (S-alkyl-L-cysteines, S-alkyl-2-methyl-DL-cysteines and their hydantoin derivatives, and sulfoxides of these compounds) were examined. E. coli cells (10(6)/ml) in 20mM aqueous solution of the sulfur compounds was irradiated with 60 Gy (6 krad) of γ-rays. Mice (5-week-old males) were subjected to 7.5 Gy (750 rad) of γ-rays after a single intraperitoneal injection of 0.75m mol/kg body weight of each compound. In the case of E.coli, S-alkyl compounds were more effective than S-propyl ones for protection, and sulfoxide amino acids exhibited a radiosensitization effect. The replacement of the α-hydrogen of S-substituted cysteines by methyl groups decreased the radioprotective effect. On the other hand, the hydantoin derivatives, such as DL-5-allylthiomethyl-hydantoin, were much more radioprotective than the original amino acids. In mice, DL-5-allylthiomethyl-5-methlhydantoin and DL-5-n-propylthiomethylhydantoin (0.75m mole/kg) had a remarkable radioprotective effect. The survival ratios were 6.33 and 6.67, or the dose reduction factors (DRF) were 1.41 and 1.53, respectively. On the other hand, DL-5-allylthiomethyl-5-methylhydantoin sulfoxide had a radiosentizing effect: survival ratio, 0.333; DRF, 0.517.