RADIATION PROTECTION BY ALPHA-METHYL-HOMOCYSTEINE THIOLACTONE IN-VITRO

The radiation protective effect of thiol compounds is unequivocal and their use is only limited by their toxic effects. We used the principl e of alpha alkylation, which renders amino acids unmetabolizable, to r educe the toxicity of homocysteine. This product, alpha-methyl-homocys teine thio-lactone, was tested for toxicity and radiation protective e ffect along with known protectors L-cysteine, cysteamine and WR 1065 i n cell culture using V79-4 Chinese hamster lung cells. The three-day g rowth curve assays, useful to measure overall effects on cell growth, revealed lowest toxicity for alpha-methyl-homocysteine thiolactone (GL -2). Clonogenic survival tests, used to evaluate the retention of repr oductive integrity, were carried out and revealed that GL-2 had no adv erse effects in this test system. Radiation protection tests showed th at GL-2 exhibited protective activity against radiation induced lethal ity above that seen with cysteine and cysteamine, but below WR 1065. H owever, GL-2 showed little or no negative effects toward the cell itse lf, in direct contrast to WR 1065. Our findings show a potentially imp ortant tool and principle to reduce toxicity of radiation protectors w ith analogous structures.