Absorption and Excretion of Zinc, Cadmium and Mercury in the Gastrointestinal Tract

Abstract

This study was undertaken to compare the absorption and excretion of inorganic zinc, cadmium and mercury in the gastrointestinal tract using⁶⁵Zn.¹⁰⁹Cd and²⁰³Hg.
A single dose of⁶⁵Zn, ¹⁰⁹Cd or²⁰³Hg 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. Every eight mice or rats were used to measure the radioactivity in sample with a scintillation counter.
Most of the orally administered⁶⁵Zn, ¹⁰⁹Cd or²⁰³Hg was excreted into feces and was less absorbed from the gastrointestinal tract, respectively. Absorption rate in the gastrointestinal tract was as follows: ²⁰³Hg>⁶⁵Zn>¹⁰⁹Cd. Intravenously injected⁶⁵Zn, ¹⁰⁹Cd or²⁰³Hg was excreted 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, and¹⁰⁹Cd 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 accumulated organ of absorbed⁶⁵Zn, ¹⁰⁹Cd or²⁰³Hg was the pancreas and liver, liver and kidney, kidney and liver, respectively.