Tissue distribution and retention of cadmium in rats during postnatal development: Minimal role of hepatic metallothionein

Abstract

Since liver concentration of metallothionein in 4-day-old rats is 20 times greater than that in 70-day-old adults, experiments were performed to determine whether the high concentration of metallothionein in the liver of newborn rats results in a greater distribution of cadmium to the liver and in subsequent lower concentration of cadmium in other tissues of the newborn in comparison to the adult, and if the retention of cadmium in the various tissues is affected. The concentration of cadmium in the liver of 4-day-old rats was only 30% higher than that in adult rats 2 hr after administration (1 mg/kg, iv). Even though there is no age difference in the renal concentration of metallothionein, the initial concentration of cadmium in the kidney of 4-day-old rats was half that in adult rats. However, cadmium was three to six times more concentrated, 2 hr after cadmium administration, in the spleen, bone, brain, testes, and muscle of newborn than in adult rats. Over a 19-day period, cadmium was similarly retained in the liver, kidney, and lung of newborn and adult rats, but the rate of cadmium elimination was higher from the heart and lower from the testes of newborn rats when compared to adults. These results indicate that metallothionein does not appear to play a major role in the tissue distribution and tissue retention of cadmium. The higher concentration of cadmium in some target organs, such as testes, kidneys, and lungs, of the newborn rat may have significant toxicological implications.