[The subchronic toxicity of 5-vinyloxazolidine-2-thione in rats]. / Untersuchung der subchronischen Toxizität von 5-Vinyloxazolidin-2-thion an Ratten.

Groups of male and female rats received 5-vinyloxazolidine-2-thione (VOT) in their drinking water for 13 weeks at concentrations of 0, 10, 25, 50 or 100 mg/l and 0, 2.5 or 5 mg/l respectively. Compared with the controls, there were decreases in food intake and growth of females given VOT-doses of 10 mg/l and higher. Liquid intake was reduced in males and females of the highest dose group. Terminal haematological examination revealed an increase in white cell count at the 50 and 100 mg levels in females and a reduction in the red cell count at 100 mg/l in males. Organ weight changes were dose-related increases in the relative thyroid and liver weight and a decrease in the relative thymus weight. Structural and functional changes of the thyroid were observed in animals at levels of 10 mg/l and higher. Histological examinations of the kidneys showed tubulonephrosis in animals at and above a VOT-level of 5 mg/l. The no-observed-effect level (NOEL) established from these studies was 2.5 ml VOT/l drinking water (approximately equivalent to an daily intake of 0.4 mg/kg body weight).

The influence of high glycine diets on the activity of glycine-catabolizing enzymes and on glycine catabolism in rats.

Male albino rats were adapted to isocaloric purified diets that differed mainly in their glycine and casein contents. Controls received a 30% casein diet. In experimental diets gelatin or gelatin hydrolysate was substituted for half of the 30% casein. An additional group was fed a glycine-supplemented diet, which corresponded in glycine level to the gelatin diet but in which the protein level was nearly the same as that of the casein control diet. Another group received a 15% casein diet. Rat liver glycine cleavage system, serine hydroxymethyltransferase and serine dehydratase activities were measured. 14CO2 production from the catabolism of 14C-labeled glycine was measured in vivo and in vitro (from isolated hepatocytes). Serine dehydratase and glycine cleavage system activities were higher in animals fed 30% casein diets than in those fed 15% casein diets. Serine hydroxymethyltransferase activity of the cytosolic and mitochondrial fractions was highest when a high glycine diet (glycine administered as pure, protein bound in gelatin or peptide bound in gelatin hydrolysate) was fed. 14CO2 formation from [1-14C]- and [2-14C]glycine both in vivo and in isolated hepatocytes was higher when a high glycine diet was fed than when a casein diet was fed. These results suggest that glycine catabolism is dependent on and adaptable to the glycine content of the diet. Serine hydroxymethyltransferase appears to play a major role in the regulation of glycine degradation via serine and pyruvate.