Effect of dose level and pregnancy on the distribution and toxicity of intravenous lead in rats.

Female Wistar rats were injected intravenously with tracer levels of 210Pb, alone or combined with carrier Pb(NO3)2 at 5 or 25 mg/kg body weight at 9 or 15 days of gestation (dg). Tissue 210Pb distribution and retention, and lead excretion, were measured several times during the first 30 h and at 20 dg. Toxic effects following the administration of 25 mg/kg (a teratogenic dose) included an early decrease in hematocrit, hematuria, gastrointestinal hemorrhage, and diarrhea, as well as an eventual loss of body weight and an increase in spleen and kidney weights. The stage of pregnancy at injection did not affect the retention and distribution of lead in major organs other than the reproductive system. Following injection of the 25-mg/kg dose, deposition of lead in the liver, kidney, spleen, and lung was elevated. Disproportionately high plasma lead levels were also observed at early times after the injection of the 25-mg/kg dose, and may act as a significant factor in placental lead transfer and subsequent malformations or fetal mortality.