The effect of consumption of glucosinolate-containing Brussels sprouts on alpha-class glutathione S-transferase levels in human blood plasma was investigated in 10 healthy, male, non-smoking volunteers. Following a 3-week run-in period, five volunteers continued on a glucosinolate-free diet during a subsequent 3-week intervention period (control group), while the other five (sprouts group) consumed 300 g of cooked Brussels sprouts per day, at the expense of 300 g of a glucosinolate-free vegetable. alpha-Class glutathione S-transferases were measured by radioimmunoassay. In the control group, similar alpha-class glutathione S-transferase levels were observed in both periods (P = 0.814), while in the sprouts group the alpha-class glutathione S-transferase levels were elevated by a factor of 1.4 (P = 0.002). We hypothesize that the elevated alpha-class GST levels in plasma reflect GST-alpha induction in tissues such as liver and small intestine under non-toxic conditions. The present findings indicate that alpha-class GST levels in plasma may be used as a biomarker for alpha-class GST levels in tissues. In addition, they support the results of epidemiologic studies that consumption of cruciferous vegetables may result in a decreased cancer risk.

Mononuclear lymphocytes were isolated from the blood of 12 individuals, who had been exposed to the vapour of the soil fumigant 1,3-dichloropropene (DCP). Western blot experiments were performed on the crude lymphocyte homogenates, using a monoclonal antibody against human hepatic glutathione S-transferase (GST) isoenzyme mu, to determine the presence or absence of mu-class isoenzymes mu and/or psi. Nine of the individuals were found to be positive for mu and/or psi, the remaining three individuals being negative. In addition, all individuals showed a positive staining on immunoblot of a protein of somewhat lower molecular mass than the hepatic standard. This protein was bound by the S-hexylglutathione affinity column, and presumably constitutes a new mu-class isoenzyme, which is not subject to genetic polymorphism. Determination of the specific activities of individual human GST isoenzymes towards Z-(cis-) and E-(trans-)-DCP demonstrated that mu-class isoenzymes show a considerably higher specific activity with Z-DCP than alpha-class or pi-class isoenzymes. In addition, mu-class isoenzymes were found to be 2- to 3-fold more active with Z-DCP than with E-DCP. Their activity towards E-DCP was similar to the specific activity of alpha-class isoenzymes. Genetic polymorphism for mu-class isoenzymes could thus be a determinant in the extent of excretion of mercapturic acids from Z- and E-DCP. The urinary excretion of Z- and E-DCP mercapturic acids and the respiratory exposure to Z- and E-DCP were determined for nine and eight phenotyped individuals, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)