The relationship of vehicle to target organ toxicology induced by the naturally occurring nitrile 1-cyano-2-hydroxy-3-butene.

The effects of gavage vehicle on the acute toxicity of the naturally occurring nitrile 1-cyano-2-hydroxy-3-butene (CHB) were investigated by oral administration of 200 mg/kg body wt/day CHB to male CDF (F-344/Crl BR) rats for 2 days. The vehicles studied here were distilled water, 5% aqueous Tween 20, and corn oil. Liver, kidney, and pancreas were examined histologically and the differences in lesion incidence and severity were assessed. The effects of gavage vehicle on nitrile-induced elevations of daily urinary thiocyanate excretion and tissue glutathione concentrations were also assessed. The pancreatotoxicity of CHB was present regardless of vehicle and consisted of apoptosis of pancreatic acinar cells, infiltration of pancreatic lobules by macrophages, and acinar atrophy and disorganization. CHB in water alone was associated with the least pancreatotoxic effect, whereas the aqueous Tween vehicle was associated with more severe CHB-induced pancreatic lesions. CHB-induced elevations of tissue nonprotein thiol and glutathione concentrations occurred in all treatment groups, but the values were elevated significantly less in the pancreata of CHB/Tween-treated rats than in those of rats given CHB in water or corn oil. By contrast, the greatest elevation in daily urinary thiocyanate excretion occurred in rats given CHB in aqueous Tween, indicating increased biotransformation of CHB to cyanide when Tween 20 was used as a vehicle. These results illustrate the difficulty of identifying suitable vehicles for administration of lipophilic compounds in toxicology studies.

Comparative toxicities of the naturally occurring nitrile 1-cyano-3,4-epithiobutane and the synthetic nitrile n-valeronitrile in rats: differences in target organs, metabolism and toxic mechanisms.

Toxic but sublethal oral doses of 125 mg/kg (1.1 mmol/kg) of the cruciferous nitrile, 1-cyano-3,4-epithiobutane (CEB), or 175 mg/kg (2.1 mmol/kg) of its synthetic saturated analogue, n-valeronitrile (VN), were given by gavage to male CDF (F-344/CrlBr) rats once daily for 1, 2 or 3 days, in order to compare target tissues and to observe structure-activity relationships between the nitriles. CEB-induced changes included degeneration and necrosis of the pars recta of the renal proximal tubules, ulceration and necrosis in the forestomach, a mild increase (4.5-fold) in daily urinary thiocyanate (SCN-) excretion (only in rats treated for 3 days) and 1.5- to 2.4-fold increases in hepatic and pancreatic non-protein thiol (RSH) concentrations (in all CEB-treated groups). In VN-treated rats, there were no consistent histological changes but 95- to 170-fold increases in daily urinary SCN- excretion, delayed clinical signs of cyanide toxicity and minimal effects on tissue RSH concentrations. These results indicate different toxic mechanisms for VN and CEB. The nephrotoxic effects of CEB were very similar to those of 1-cyano-2-hydroxy-3,4-epithiobutane, suggesting a role for the epithio group in the nephrotoxicity of these nitriles. The relatively low SCN- excretion in CEB-treated rats also suggested that cyanide played only a minimal role in CEB toxicity, while the high SCN- excretion, clinical signs of cyanide poisoning and lack of histological changes imply a greater role for metabolically-derived cyanide in VN toxicity. The enhancement of tissue RSH by CEB treatment with indications of enhanced tissue glutathione concentrations suggested the involvement of glutathione in the detoxication of CEB and/or its reactive metabolites.

Selective pancreato-toxicity in the rat induced by the naturally occurring plant nitrile 1-cyano-2-hydroxy-3-butene.

The acute toxicity of 1-cyano-2-hydroxy-3-butene (CHB), a nitrile derived from many cruciferous plants, was investigated. Young male CDF (F-344/CrlBr) rats were treated by gavage once daily with 200 mg (2.1 mmol) CHB/kg body weight for 0-4 days and killed 24 hr after the final dose. Lesions were confined to the exocrine pancreas and characterized by individual acinar cell death, inflammation and acinar atrophy and disorganization. Ultrastructural alterations included dilation of cisternae of the acinar cell endoplasmic reticulum, acinar cell death resembling apoptosis, macrophage phagocytosis of acinar cell debris and regenerative changes in remaining acinar cells. Pancreatic, hepatic and renal non-protein thiol concentrations were elevated, suggesting an enhancement of tissue glutathione concentrations and an alteration in glutathione metabolism. Urinary thiocyanate (SCN-) excretion was modestly elevated, indicating some in vivo cyanide release from this nitrile. The results of this study indicate that CHB is a selective pancreatotoxin, inducing changes consistent with apoptosis. CHB is also a possible inducer of tissue glutathione in the liver and kidneys as well as in the pancreas, even at toxic doses.

Clastogen-induced micronuclei in peripheral blood erythrocytes: the basis of an improved micronucleus test.

Micronuclei induced in bone marrow erythroblasts by clastogenic chemicals are easily detected in peripheral blood. In mice treated with nitrogen mustard, 7,12 dimethylbenz(a)anthracene, or cyclophosphamide, the peak incidence of micronucleated polychromatic erythrocytes in peripheral blood was at least as great as the maximum incidence in bone marrow. In each case the peak incidence in blood occurred on the day following the peak incidence observed in bone marrow. Thus, for general genetic screening purposes, monitoring micronuclei in peripheral blood rather than in bone marrow smears provides at least equal sensitivity, offers greater simplicity in sample preparation and scoring, permits multiple sampling of treated animals, and may also facilitate automated scoring and human cytogenetic monitoring.

Mutagenicity tests of diflubenzuron in the micronucleus test in mice, the L5178Y mouse lymphoma forward mutation assay, and the Ames Salmonella reverse mutation test.

Diflubenzuron, one of a new class of pesticides believed to act via inhibition of chitin synthesis in the developing insect cuticle, was tested for possible mutagenic activity using the micronucleus test in mice, the L5178Y mouse lymphoma forward mutation test at the thymidine kinase locus, and the Ames Salmonella/microsome reverse mutation test. No mutagenic effect was found.