This study aims to evaluate the effect of solar UV radiation on defensive enzymes activities in lettuce seedlings. Seeds of lettuce were grown in high tunnels for 35 days, exposed to three different levels of solar UV, created by using three different types of plastic films. Each plastic film transmits different levels of solar UV (0% in UV-B, 4% in UV-L and 83% in UV-T). The obtained results indicated that solar UV radiation has led to significant decrease in seedling fresh weight. UV-B treatment resulted the highest shoot and root length while UV-T treatments exhibited the highest shoot: root ratio. Solar UV radiations have no effect on peroxidase activity in shoots. While ascorbate peroxidase was activated and catalase was inhibited in shoot by UV-T treatments. In lettuce roots, peroxidase, ascorbate peroxidase, and catalase activities were increased by increasing the level of solar UV radiation. In case of UV-T, phenylalanine ammonia lyase (PAL) activity in both shoots and roots of lettuce seedlings was higher than those of other treatments. In addition, Phenols are accumulated in lettuce shoots as a result of UV radiation in UV-L and UV-T treatments. Also, phenols in roots increased by increasing solar UV dose. The study concluded that solar UV radiation induced some antioxidant enzymes, increased the accumulation and biosynthesis of phenolic compounds and reduced lettuce seedlings growth.

The protective effect of folic acid (FA) on he-patic oxidative stress in aged rats exposed to oxi-dative stress by supply drinking water with 1% H2O2 (v/v) was studied. Rats were divided into two groups, the first group was considered as standard one (F1) which was fed on basal diet and administrated 1 mg FA/ Kg body weight (BW) daily by stomach tube without addition H2O2 in drinking water. The second group was divided into five subgroups, the first subgroup was the control (F2) which fed on basal diet free from folic acid (FF) with 1 % H2O2 in the drinking water, while other groups from F3 to F6 were adminis-trated different concentrations of folic acid (1, 20, 40 and 80 mg FA/ Kg BW), respectively. Weight gain, total feed intake, feed efficiency, liver weight and its relative weight were estimated. Bi-ochemical assay: activity of antioxidant enzymes system such as superoxide dismutase (SOD), cata-lase (CAT); lipid peroxidation level as malondial-dehyde (MDA), hydrogen peroxidase (H2O2); and liver functions [alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phos-phatase (ALP) and gamma glutamyl transferase (γ-GT), and lactate dehydrogenase (LDH)], were determined. Additionally, total protein (TP), al-bumin, globulin, A/G ratio, total bilirubin, direct bilirubin, indirect bilirubin; and kidney functions [creatinine, urea, and uric acid]; and lipid profile as [total cholesterol, HDL-cholesterol and LDL-cholesterol, and triglycerides] were also, carried out. The obtained results showed accumulated weight gain which significantly increased in rats group administrated 40 and 80 mg/ Kg BW/d folic acid. No changes in relative liver weight among tested rat groups were recorded. No significant difference was observed in lipid profile, LDH and SOD between groups (F1 and F6). Data also indi-cated that F1 group recorded the best one which was low in MDA and high in CAT, followed by F6. Folic acid showed no effect on kidney func-tions. No histopathological changes were observed in liver of rat groups administered 40 or 80 mg folic acid / Kg BW/d, thus indicating that supple-mentation with high doses of FA had a protective effect from the hepatic oxidative stress in liver of tested rats.

The interactions between dietary zinc, copper and iron and their effects on antioxidant enzymes activity [superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST)] were examined. Fifty-four rats weighting approximately between 80-100 grams were divided into nine groups (E1- E9). Each group containing six rats was fed on basal diet with varying amount of Zn (2.5, 35 or 175 mg Zn/kg diet), Cu (1.2, 6.3, or 25 mg Cu/kg diet) and Fe (10, 50 or 230 mg Fe/kg diet). The second group (E2) was fed a diet defi-cient in all studied elements (2.5mg Zn, 1.2mg Cu, and 10mg Fe per 1 kg diet). The results of E2 showed a decrease in SOD and CAT activity and increase GST in plasma erythrocytes and tissues. Moreover, plasma thiobarbituric acid reactive sub-stances (TBARs) and hydrogen peroxide produc-tion in E2 were found to be higher than those in other groups. The high activity of lactic acid de-hydrogenase (LDH) in the plasma indicated that cell membrane damage was occurred. This dam-age was accompanied by elevation of lipid peroxi-dation and in the same time by reduction of SOD and CAT activity. Supplementation of basal diet with the different concentrations of studied miner-als led to improve the activity of antioxidants en-zymes (SOD and CAT) and decrease in TBARs and LDH activity.