COMPARISON OF EFFECTS OF 0.5 AND 3.0 GY X-IRRADIATION ON LIPID-PEROXIDATION AND ANTIOXIDANT ENZYME FUNCTION IN RAT TESTIS AND LIVER

The prooxidant effect of X-irradiation on rat testis and liver tissue was studied with doses of 0.5 and 3.0 Gy; the latter dose kills the pr oliferating spermatogonia and causes a maturation-depletion process in the germ cells. The level of lipid peroxidation, measured by the form ation of diene conjugates and thiobarbituric acid-reactive substances (TBARS) and the activities of the antioxidant enzymes were determined 0.5 hours, 1 day, 7 days, and 31 days after the exposure. In the liver , increased levels of diene conjugation (+36%, P < 0.05) in the group of 3.0 Gy at 0.5 hours indicated increased lipid peroxidation. At the same time, TBARS were increased (+25%, P < 0.05) in the group of 0.5 G y, but not in the 3.0-Gy group. In the testis, diene conjugation was n ot determined at 0.5 hours postirradiation, and at day 1 it was at the control level. The level of TBARS in the testis was below control (-1 1%, P < 0.01) in the 3.0-Gy group at day 1. At day 31 after 3.0 Gy in the testis, an increase in the amount of conjugated dienes (+24%, P < 0.01) was observed in parallel with a decreased level of TBARS (-15%, P < 0.01). The activity of superoxide dismutase (SOD) was decreased in the testis at 0.5 hours postirradiation (-28%, P < 0.05, and -29%, P < 0.05, in the groups of 0.5 and 3.0 Gy), whereafter it returned to no rmal by day 7. In the liver, such inactivation of SOD was not observed . At day 1 postirradiation, a decreased level of catalase activity was detected in the liver (-18%, not significant, and -26%, P < 0.05) but not in the testis. Inductions of glutathione transferase (GSH-Tr) in the testis (+31%, P < 0.05, and +38%, P < 0.01) and glutathione peroxi dase (GSH-Px) in the liver (+26%, P < 0.05, and +33%, P < 0.01) were s een at day 7. By day 31, increased levels of GSH-Px (+32%, P < 0.05) a nd GSH-Tr (+41%, P < 0.01) were observed in the testis after 3.0 Gy bu t not after 0.5 Gy. In this study, the changes in diene conjugates are suggested to reflect changes in lipid peroxidation, whereas those in TBARS are not. SOD activity of rat testis was found to be sensitive to inactivation by 0.5 and 3.0 Gy X-irradiation, which makes testis vuln erable to oxidative stress. In addition, germ cell depletion 31 days a fter 3.0 Gy increased the level of lipid peroxidation and the activiti es of lipid peroxide detoxifying enzymes GSH-Px and GSH-Tr in the rat testis. In the rat liver, 3.0-Gy X-irradiation leads to a transient in crease in lipid peroxidation, but SOD is not inactivated.