DISTRIBUTION OF N-13 FROM LABELED NITRATE NO3-(N-13) IN HUMANS AND RATS

The body distribution of gavaged or intravenously administered nitrate labeled with nitrogen-13 was studied in humans and rats with the following results: (i) the labeled compound is not quickly absorbed from the stomach; (ii) the concentration of the label increases inside the lower intestinal tract (cecum and large intestine) when ingested or intravenously injected; and (iii) humans and rats have the capacity to store a portion of the label in their bodies. These observations indicate that depletion of body stores, the passage of nitrate down the gut, or the secretion of nitrate into the intestinal lumen may be a better explanation of the urinary, ileal, and fecal concentrations of nitrate and nitrite recently measured in humans than a bacterial nitrification reaction in the intestines, as suggested by Tannenbaum et al. (12). Copyright © 1979 AAAS.