Radioprotective effect of 2-mercaptopropionylglycine on radiation-induced microsomal lipid peroxidation.

Radiation-induced microsomal lipid peroxidation was measured following gamma-irradiation (66-399 Gy) in the presence or absence of 2-mercaptopropionylglycine (MPG) at low and high concentrations (0.03 and 0.1 mg/ml). At high concentrations of MPG, enhancement of lipid peroxidation was observed instead of reduction. Following gamma-irradiation at 266.4 Gy, lipid peroxidation increased with increasing concentrations of MPG. The spontaneous lipid peroxidation also increased with increasing concentrations of MPG. When MPG and EDTA were added together, radioprotection was observed even at high concentrations of MPG after different doses of radiation. An increase in radioprotection with increasing concentrations of MPG in the presence of EDTA at 266.4 Gy was also observed. The exogenous supply of Fe2+ during irradiation was found to eliminate the 'threshold dose' which has to be delivered before MPG shows an 'enhancement effect'. A possible mechanism for the enhancement of radiation-induced lipid peroxidation is proposed.