Absorption and excretion of zinc, cadmium and mercury in the gastrointestinal tract

The absorption and excretion of inorganic zinc, cadmium and mercury in the gastrointestinal tract were compared using 65Zn, 109Cd and 203Hg. A single dose of 65Zn, 109Cd or 203Hg was administered orally or injected intravenously to investigate the distribution, excretion into bile and excretion into feces or urine. Absorption and excretion through the gastrointestinal tract of mice were studied by the tied loop method. Groups of eight mice or rats were used to measure the radioactivity in sample with a scintillation counter. Most of the orally administered 65Zn, 109Cd or 203Hg was excreted into feces and was less absorbed by the gastrointestinal tract, respectively. Absorption rate in the gastrointestinal tract was as follows: 203Hg>65Zn>109Cd. Intravenously injected 65Zn, 109Cd or 203Hg was escreted into the gastrointestinal tract through the gastrointestinal wall and bile duct, respectively. Excretion rate in the gastrointestinal tract was as follows: 65Zn>203Hg>109Cd. When comparing the absorption and excretion in each gastrointestinal tract divided into 10 parts, 65Zn, and 109Cd were relatively well absorbed from the upper and lower part of small intestine and excreted into the upper, middle, lower part. 203Hg was relatively well absorbed from the upper, lower part of small intestine and excreted into the stomach and the caecum. The major organs that accumulated absorbed 65Zn, 109Cd or 203Hg were the pancreas and liver, liver and kidney, kidney and liver, respectively. (auth.)