INTESTINAL-ABSORPTION AND URINARY-EXCRETION OF MELAMINE IN MALE WISTAR RATS

Intestinal distribution and absorption of melamine and the disposition of this compound in blood and urine were examined in Wistar male rats. When rats were fed a diet containing 1% melamine for one week, the concentration of melamine in the stomach contents was 3,040 +/- 772 ppm. The concentration of melamine was highest in the upper part of the small intestine, 487 +/- 101 ppm, and it decreased gradually along the intestines, being 158 +/- 20.0 ppm in the lowest part. But there was more melamine in the cecum and the large intestine: 193 +/- 38.8 ppm and 283 +/- 20.3 ppm, respectively. Further, 22.6 +/- 6.93 ppm and 5,050 +/- 2,010 ppm of melamine appeared in the blood and urine, respectively. Melamine was not absorbed in the stomach but was absorbed monoexponentially in the small intestine. Its half life in the ligated upper part of the small intestine was 37.9 min. The doubling time of melamine was 18.6 min in the blood and 2.9 min in urine. Melamine injected into a femoral vein was excreted monoexponentially into urine from blood. The excretion was suppressed between 15 and 20 min after the injection, then resumed monoexponentially after 20 min.