Cadmium-induced fetal growth retardation: Protective effect of excess dietary zinc

Abstract

Reproductive performance and fetal cellular growth and development were investigated in laboratory rats chronically fed low drinking water levels (0, 1.0, 10.0, and 100 μg/ml) of cadmium (Cd), a known embryotoxic trace element, through gestation. Maternal daily food and water consumption, total weight gain, maternal weight gain, and feed efficiency all decreased with increasing Cd consumption. Term fetal weight was significantly less than that of control subjects only in the group fed 100 μg Cd/ml drinking water. Total litter weight, however, gradually decreased with increasing Cd concentration due to reduced litter size. Fetal growth retardation was a result of decreased cell division (DNA) and cell growth (protein/DNA ratio). When dams were pair-fed the average daily amount of food consumed by those fed 100 μg Cd/ml drinking water, maternal weight gain and fetal weight, DNA, and protein/DNA ratio were increased, but not to control levels. Dietary zinc (Zn) supplementation (5.0 μg/ml drinking water) of Cd-fed dams increased maternal food consumption and fetal weight, DNA, and protein/DNA ratio to control levels. Fetal levels of Cd were extremely low (0.038 to 0.095 μg/gm fetus) and did not increase with increasing Cd consumption, while placental Cd increased more than 10-fold. Fetal Zn was decreased in Cd-fed dams, and Zn supplementation increased fetal Zn levels, but not to control levels. These results suggest that Cd-induced fetal growth retardation is an indirect rather than a direct effect, resulting from reduced maternal food consumption and metabolism. Since dietary Zn blocks these effects, Cd may be a result of induced Zn deficiency.