The effect of three NaNO2 concentrations (0.5, 2.0, and 5.0 mM) on 15N-ammonia utilization, ureagenesis, glucose, pyruvate and lactate formation and glycogen breakdown were studied in isolated rat hepatocytes. Nitrite failed to affect the rate of glycogenolysis as well as the lactate and pyruvate formation, but at the same time it markedly increased the glucose formation. It is concluded that the increase in the glucose formation results from the nitrite stimulation of the rate of gluconeogenesis. An increased sodium nitrite concentration caused a significant decrease in the ammonia utilization and urea synthesis; there are strong linear correlations between the nitrite concentration and the amount of utilized ammonia (r = -0.93) and the formed urea (r = -0.96). The observed lower rate of ureagenesis in the presence of nitrite resulted from the diminished incorporation of the added 15N-ammonia into urea, as well as from the diminished urea formation from endogenous nitrogen. It is concluded that the disturbances in carbohydrate and nitrogen metabolism observed in the nitrite-poisoned animals are attributed to the direct effect of nitrite on metabolism.
The method of isotope dilution for the determination of endogenous N-secretion was used with three pigs of a live weight of between 15 and 27 kg, which were provided with simple cannulae at the end of the small intestines. The test animals received a single dose of a semi-synthetic ration with 15N-labelled dried curds as sole source of protein. The passage rate to the ileum ascertained with the help of 51Cr2O3 was 70% in 24 hours. During the test period of 24 hours the endogeneous N-amount in the ileum chyme was 1.11 g resp. 56.6 mg/kg live weight. Of that, 60% were allowed to be absorbed in the chyme at the end of the small intestine.
The amount of endogenous N in the chyme at the end of the small intestine and the amino acid composition of the ileum chyme were ascertained with growing pigs with ileorectostomy after feeding qualitatively differentiated protein sources. In dependence on the protein used, distinct differences turned out for some amino acids with regard to their content in the ileum chyme. Bacteriologic and histologic investigations subsequent to the dissection of the test animals showed that - in comparison to the control animals-the functions of the small intestine remained the same during the time of the experiment. The experiment method described appears to be suitable for absorption investigations up to the end of the small intestine of growing pigs.
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