lead-radioisotopes and lead-chloride

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.

Topics: Animals; Autoradiography; Brain; Injections, Intravenous; Kidney; Lead; Lead Radioisotopes; Male; Mice

The radionuclide 203Pb decays completely by electron capture to stable 203Tl with a half-life of 52 h. The primary radiation from the decay is gamma-ray radiation 280 keV (80%). 203Pb is produced easily from the natural metal thallium by the method described below. 203Pb-chloride is a promising imaging agent for tumour scanning because of the large retention value for tumour tissue and the small value for normal organs, but the large value for the kidney and bone is a shortcoming when considering it as an imaging agent. The retention value of 203Pb in tumour tissue is larger than that of 201Tl and smaller than that of 67Ga. The tumour/inflammatory lesion retention ratio for 203Pb is very large in comparison with those for 67Ga and 201Tl. 203Pb accumulates to a large extent in viable tumour tissue, and less in necrotic tumour tissue and in inflammatory lesion. Therefore, 203Pb-chloride is far better for visualization of viable tumour tissue than 67Ga and 201Tl if the large retention values for the kidney and bone were reduced.

Topics: Animals; Citrates; Citric Acid; Gallium Radioisotopes; Lead; Lead Radioisotopes; Male; Rats; Sarcoma, Experimental; Thallium; Thallium Radioisotopes

Absorption of lead is known to be enhanced during infancy. In this study, the sites of intestinal accumulation of Pb by suckling rats have been determined under various conditions using 203Pb as a tracer. When 203Pb was administered intragastrically (IG) as a soluble salt, accumulation occurred primarily in the duodenum, regardless of dose and vehicle. In contrast, when rat pups suckled from a dam which had received 203Pb, the only region of the small intestine showing accumulation of radioactivity was the ileum. To confirm that these differences were not related to the route of administration, rat milk was labeled with 203Pb and was then used for IG administration. Once again, accumulation (4 hr post-administration) was confined to the ileum. When the dose was increased 10-fold, milk Pb displayed some accumulation in duodenal tissue, but very much less than that of soluble Pb at the same time and dosage. At 20 hr postadministration, there was negligible 203Pb in any region of the small intestine following administration as a soluble salt, but substantial retention in ileal tissue following administration in milk. The strikingly different patterns of intestinal accumulation obtained with Pb salts as compared with milk Pb suggest different modes of absorption of Pb ingested in these two forms.

Topics: Animals; Animals, Suckling; Duodenum; Ileum; Intestinal Absorption; Lead; Lead Radioisotopes; Milk; Rats; Rats, Inbred Strains; Tissue Distribution