Buthionine sulfoximine prevents the reduction of the genotoxic activity ofmaleic hydrazide by soil humic substances in Vicia faba seedlings

A significant reduction of the genotoxic effects caused by herbicide maleic hydrazide (MH) in Vicia faba seedlings was observed to be induced by a gro wth step in an organic soil as well as by a pretreatment with highly purifi ed humic substances. In addition, such protective activity was resulted qui te similar to that observed when the conditioning pretreatment was carried out with metal salts, so suggesting the involvement of the GSH biosynthesis in determining the protective activity observed. In agreement with this hy pothesis, a previous exposure to buthionine sulfoximine (BSO), an inhibitor of the phytochelatins production, through the inhibition of GSH synthesis, prevented the reduction of the genotoxic activity of MH. The findings prov ide evidence for the involvement of the GSH biosynthesis pathway in determi ning the antigenotoxic activity revealed and suggest a possible involvement of the phytochelatins in this process. However, yet to be clarified is whe ther the stimulation of GSH production results as a consequence of a nonspe cific influence on the protein synthesis by humic substances or of its dire ct activation due to the presence, as contaminants, of some heavy metals in both organic soil and humic acids extracts. (C) 1999 Elsevier Science B.V. All rights reserved.