Chemical Determination of Methylnitrosourea and Ethylnitrosourea in Stomach Contents of Rats, After Intubation of the Alkylureas Plus Sodium Nitrite 2
- 1 March 1973
- journal article
- research article
- Published by Oxford University Press (OUP) in JNCI Journal of the National Cancer Institute
- Vol. 50 (3) , 745-750
- https://doi.org/10.1093/jnci/50.3.745
Abstract
A method was described for determining >0.2 mg amounts of methylnitrosourea (MNU) or ethylnitrosourea (ENU) in rat stomach contents or powdered rat food. The method involved hexane extraction, ether extraction from a methanol-water mixture, a second ether extraction after removal of the methanol, thin-layer chromatography, and determination of the nitrosoureas by ultraviolet absorption. Starved rats were given 21.5 mg methylurea or 25.5 mg ethylurea plus 10 mg NaNO2 by stomach tube. After 45–80 minutes the stomach contents showed a mean yield from nitrite of 27% for MNU and 8.7% for ENU (7 rats each). Intubation of sodium bicarbonate before the methylurea and nitrite were given neutralized the stomach contents and prevented MNU formation. MNU was stable when incubated with gastric juice for 1 hour at 37° C. Thirty minutes after intubation of 5 mg MNU or ENU, 27–29% of the nitrosoureas were recovered from the stomach. This is the first demonstration by chemical analysis of nitrosourea formation in the stomach. Estimates based on the nitrosation kinetics indicated that the nitrosoureas could reasonably be formed by an acid-catalyzed chemical reaction.Keywords
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