Chronic low-level lead toxicity in the rat: I. Maternal toxicity and perinatal effects

The first in a series of studies on the chronic exposure of rats to lead (Pb) is reported here. Weanling females were provided semipurified diets containing no detectable Pb, and drinking water containing 0, 0.5, 5, 25, 50, or 250 ppm Pb (as Pb-acetate). Rats were exposed to Pb-acetate for 6–7 weeks, then mated and exposed continuously throughout gestation and lactation. No statistically significant change in food or water consumption was noted in any exposure group. Females in the 50- and 250-ppm groups exhibited significant growth retardation within 1 to 3 weeks after exposure began. In addition, vaginal opening was significantly delayed in the 50- and 250-ppm groups, and to a lesser extent in the 25-ppm group. The level of Pb exposure used here did not affect the ability to conceive, to carry a normal litter to term, or to deliver the young. The percentage of malformed fetuses, resorptions, and postpartum pup deaths to weaning were unaffected by Pb exposure. Body lengths of female offspring in the 250-ppm exposure group were significantly shorter than those of controls, and there was a tendency for all young in this group to be smaller. The estimated dose of Pb consumed (mg/kg) indicated that groups were exposed to different amounts of Pb, and tissue (blood, brain, and bone) Pb concentrations indicated dose-related patterns. Urinary aminolevulinic acid concentrations were significantly dose related and were significantly correlated with blood Pb concentrations. Maternal toxicity occurred in groups exposed to 25 ppm Pb or higher and was associated with a minimum blood Pb concentration of 20 μg/dl.