Increased frequencies of diploid sperm detected by multicolour FISH after treatment of rats with carbendazim without micronucleus induction in peripheral blood erythrocytes.

The purpose of the present study was to determine the effect of a single oral dose of carbendazim (CARB) on the frequencies of numerical chromosome aberrations in sperm and on micronuclei in peripheral blood erythrocytes of rats. Dual colour FISH on epididymal sperm of rats treated 31 days before sacrifice (0, 50, 150, 450 and 800 mg/kg body wt CARB in corn oil), corresponding to exposure during late pachytene, revealed a clear induction of diploid sperm. Induction of aneuploid sperm was not observed. Although the absolute frequencies of diploidy were low, ranging from 0.03% in the control group to 0.22% in the highest dose group, the observed dose-response relationship was highly significant. In sperm of rats killed 50 days after treatment with CARB (corresponding to exposure of spermatogonial stem cells) the effect was no longer apparent. In a second experiment, in addition to more dose groups in the low dose range, the peripheral blood micronucleus assay was incorporated. Results of triple colour FISH on epididymal sperm of rats treated with CARB (0-800 mg/kg body wt) again showed induction of diploid, but not of aneuploid sperm. Induction was less prominent than in the first experiment, but the dose-response relationship for diploidy was again significant. In blood samples drawn from the tail vein 48 h after treatment with CARB induction of micronuclei in peripheral blood erythrocytes was not observed, whereas the micronucleus frequency was significantly increased after a single i. p. dose of mitomycin C (3 mg/kg body wt). In conclusion, the present results show that CARB induces diploidy in sperm, without an accompanying induction of micronuclei in erythrocytes. This finding suggests that in rats the peripheral blood micronucleus assay is a less sensitive indicator for the genotoxic potential of CARB than the epididymal sperm aneuploidy/diploidy assay.

Effects of dietary anticarcinogens on rat gastrointestinal glutathione S-transferase theta 1-1 levels.

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.

Effects of dietary anticarcinogens on rat gastrointestinal glutathione peroxidase activity.

Several naturally occurring and synthetic food components reduce gastrointestinal cancer. Many of these compounds are scavengers of free radicals, formed during oxidative stress. Glutathione peroxidases (GPxs) protect against free radicals by catalysing their inactivation, thereby consuming glutathione (GSH). This might be one of the mechanisms leading to cancer prevention. We studied the effect of several dietary anticarcinogens on gastrointestinal GPx enzyme activities in male Wistar rats. Total as well as selenium-dependent and non-selenium-dependent GPx (t-GPx, Se-GPx and nSe-GPx) enzyme activities were determined in cytosolic fractions of oesophagus, gastric and colonic mucosa and liver. d-Limonene induced all three types of GPx activities in the oesophagus. d-Limonene and PEITC induced colonic t-GPX and nSe-GPx activity. beta-Carotene induced all three colonic GPx activities and hepatic t-GPx and Se-GPx activity. Coumarin and alpha-tocopherol induced gastric t-GPx and colonic nSe-GPx activity. Oltipraz enhanced oesophageal and gastric t-GPx and oesophageal, gastric and colonic Se-GPx. All other anticarcinogens induced one type of GPx activity at one site. In conclusion, the specific enhancement of GPx enzyme activities by dietary anticarcinogens might lead to a more efficient reduction of organic hydroperoxides and hydrogen peroxide and thus add to prevention of carcinogenesis in these organs.