A high intake of glucosinolate-containing cruciferous vege tables, such as Brussels sprouts (Brassica oleraceae), has been linked to a decreased cancer risk, but the underlying mechanism is still unclear. The aim of this study was to reveal possible modulating effects of consumption of Brussels sprouts on duodenal, rectal and lymphocytic (i) glutathione S-transferase (GST) enzyme activity, (ii) GST isozyme levels and (iii) glutathione (GSH) content. Ten healthy non-smoking volunteers were randomly assigned to two groups in a cross-over design. Five persons started on a glucosinolate-free diet (control period), while the other five consumed 300 g/day cooked Brussels sprouts, at the expense of 300 g glucosinolate-free vegetables (sprouts period). After 7 days the regimen was changed for a further week. At the end of both periods blood samples and duodenal and rectal biopsies were taken. Mean GST activity showed marked differences between duodenal, rectal and lymphocytic cytosols (737 ± 54, 321 ± 29 and 154 ± 14 nmol/min/mg protein respectively), but was uninfluenced by the dietary regimen. Isozyme distribution varied greatly between the tissues. In duodenum GST-a, -7C and -[i iso zymes were expressed in considerable amounts (8441 ± 1365,3002 ± 223 and 536 ± 248 ng/mg protein respectively). Rectal biopsies also contained above three GST classes, but here GST-n was the most pronounced expressed isozyme (2849 ± 246) followed by GST-|n (495 ± 242), while GSTa was only present in minor quantities (149 ± 31). In lymphocytes only GST-71; (755 ± 96) and GST-p, (83 ± 54) could be detected. As a result of the dietary regimen rectal GST-a and -71 levels were slightly increased at the end of the sprouts period, by 30 and 15% respectively. GSH contents were uninfluenced by the dietary regimen. In conclusion, consumption of glucosinolate-containing Brussels sprouts for 1 week results in increased rectal GST-a and -tc isozyme levels. We hypothesize that these enhanced detoxification enzyme levels may partly explain the epidemiological association between a high intake of glucosinolates (cruciferous vegetables) and a decreased risk of colorectal cancer.

The effects of consumption of glucosinolate-containing Brussels sprouts on plasma and urinary glutathione S-transferase (GST) class-alpha and -pi were investigated. Five male and five female non-smoking volunteers were randomly assigned to two groups in a crossover design. Five persons started on a glucosinolate-free diet (control period), while the other five consumed 300 g of cooked Brussels sprouts per day, at the expense of 300 g of glucosinolate-free vegetables (sprouts period). Dietary regimes were reversed after 1 week. GST levels were measured by enzyme-linked immunoabsorbent assay. At the end of the sprouts period, a significant increase (1.5-fold) in plasma class-alpha GST levels was observed in males but not in females (control versus sprouts, paired t-test; P-values 0.031 and 0.317 respectively), while plasma GST class-pi levels as well as secretion of urinary GST class-alpha and -pi levels remained unchanged. We conclude that (i) increased plasma GST class-alpha levels in males originate probably solely from the liver and not from stomach, intestine or kidney; (ii) males are more susceptible for induction of hepatic GSTs than females; and (iii) urinary GST concentration seems less useful as a biomarker for hepatic GST induction.

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Several naturally occurring food components or non-steroidal anti-inflammatory drugs (NSAIDs) may reduce gastrointestinal cancer rates. Recently we have shown that dietary administration of such compounds enhanced the glutathione S-transferase (GST) enzyme activity and class alpha, mu and pi isoenzyme levels in the rat gastrointestinal tract. Elevation of the levels of GSTs, a family of biotransformation enzymes with many functions such as detoxification of carcinogens, might be one of the mechanisms that lead to cancer prevention. We therefore investigated whether the anticarcinogens alpha-angelicalactone, alpha-tocopherol, beta-carotene, coumarin, ellagic acid, flavone, indole-3-carbinol, d-limonene, oltipraz, phenethylisothiocyanate (PEITC) and the sulphoraphane analogue compound-30 affect gastrointestinal rGSTT1-1 protein levels in male Wistar rats. rGSTT1-1 protein levels were determined in cytosolic fractions of liver and oesophageal-, gastric-, small intestinal- and colonic mucosa by densitometrical analyses of western blots after immunodetection with an anti human GSTT1-1 monoclonal antibody, that cross-reacts with rGSTT1-1. In control Wistar rats, gastrointestinal rGSTT1-1 protein levels were highest in the liver and decreased in the order liver > stomach > colon > oesophagus > small intestine. Gastric rGSTT1-1 protein levels were enhanced by alpha-angelicalactone, alpha-tocopherol, coumarin, ellagic acid, oltipraz, PEITC and the sulphoraphane analogue compound-30. Oesophageal rGSTT1-1 protein levels were elevated by a-angelicalactone and coumarin, whereas colonic rGSTT1-1 protein levels were elevated by coumarin. Ellagic acid, on the other hand, reduced hepatic rGSTT1-1 protein levels to 53% of the control. In conclusion, dietary anticarcinogens are capable of inducing rGSTT1-1 protein levels in the rat gastrointestinal tract, and are most pronounced in the stomach. Enhanced rGSTT1-1 protein levels might lead to an increase of enzyme activity and to a more efficient detoxification of carcinogens and thus could contribute to prevention of carcinogenesis.

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