REGIONAL DISTRIBUTION OF (PBCL2)-PB-203 IN THE MOUSE AFTER INTRAVENOUS-INJECTION

Lead is a known neurotoxicant, and concentrations of lead in the CNS a fter acute exposure to low doses have not been studied in detail. In t his investigation, the temporal distribution of lead ([Pb-203]), injec ted intravenously at no-carrier-added (NCA) (0.6 - 0.7 mu mol/kg) and at carrier - added (7.0 - 62.3 mu mol/kg) levels was determined in mic e. Concentrations of[Pb-203] were measured in major organs and in diff erent regions of the brain. Ex-vivo autoradiographic visualization was used to confirm and extend the brain distribution findings. Results: The highest concentrations of NCA [Pb-203] were observed initially in the kidneys (52% of the injected dose (ID)/g at 1 hr) and liver (70.5% 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 afte r 24 hr and 68% at 48 hr. interestingly, in the mouse brain, the highe st levels of [Pb-203] were noted in the area of the hypothalamus. At a ll times between 30 min and 16 hr postinjection, and at ail Pb dose le vels injected the accumulation of [Pb-203] in the hypothalamic region exceeded that in all other brain regions examined. Autoradiography per formed at the 16 hr time point confirmed the high uptake and strong re tention of [Pb-203] by the hypothalamus. These studies afford new insi ght into the distribution of acutely administered lead in the brain, a nd may have implications for the understanding of some of the neurotox ic effects of lead. (C) 1998 Intox Press, Inc.