Regional distribution of 203PbCl2 in the mouse after intravenous injection

Lead is a known neurotoxicant, and concentrations of lead in the CNS after acute exposure to low doses have not been studied in detail. In this investigation, the temporal distribution of lead ([203Pb]), injected intravenously at no-carrier-added (NCA) (0.6-0.7 mumol/kg) and at carrier-added (7.0-62.3 mumol/kg) levels was determined in mice. Concentrations of [203Pb] were measured in major organs and in different regions of the brain. Ex-vivo autoradiographic visualization was used to confirm and extend the brain distribution findings.

The highest concentrations of NCA [203Pb] were observed initially in the kidneys (52% of the injected dose (ID)/g at 1 hr) and liver (10.5% ID/g at 30 min). Uptake into bone occurred gradually, reaching 25% ID/g at 24 hr. In accord with previous reports, excretion of the tracer was very slow. Approximately 80% of total ID remained in the body after 24 hr and 68% at 48 hr. Interestingly, in the mouse brain, the highest levels of [203Pb] were noted in the area of the hypothalamus. At all times between 30 min and 16 hr postinjection, and at all Pb dose levels injected, the accumulation of [203Pb] in the hypothalamic region exceeded that in all other brain regions examined. Autoradiography performed at the 16 hr time point confirmed the high uptake and strong retention of [203Pb] by the hypothalamus. These studies afford new insight into the distribution of acutely administered lead in the brain, and may have implications for the understanding of some of the neurotoxic effects of lead.