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Absorption and Tissue Distribution of Lead in Thiamin-Replete and Thiamin-Deficient Rats¹

Comparative Animal Research Laboratory, Oak Ridge, TN 37830 and Department of Animal Science, University of Tennessee, Knoxville, TN 37916

Previous experimental results revealed that thiamin (vitamin B₁) reduced lead (Pb) toxicity in calves and decreased tissue lead content in lead-treated calves and rodents. The objective of this experiment was to study the uptake and tissue distribution of lead in rats deprived of thiamin or given excess thiamin and to determine the effect of thiamin on lead absorption. Rats were divided into four groups and fed a thiamin-deficient or thiamin-supplemented diet. The thiamin-replete group also received daily injections of thiamin hydrochloride. Experimental diets were fed for 5 weeks, after which the rats were administered 10 µCi of ²⁰³Pb acetate (25 µg lead) and killed 6, 24, 48 or 72 hours later. Lead content and concentration of tissues increased twofold in the thiamin-replete group at 24 hours after dosing, but returned to control values 24 hours later. Tissue lead concentration of the thiamin-depleted group was slightly depressed at 24 hours after dosing, but this trend was reversed at the end of the experiment. Tissue lead concentrations in the pair-fed control group were three to seven times greater than in the other treatment groups 6 hours after dosing. The results indicate that thiamin facilitated absorption and increased the amount of lead initially taken up by tissue. Thiamin may also promote more rapid release of lead from tissues.

KEY WORDS: • lead • thiamin • rat

¹ Work supported by Environmental Protection Agency-Department of Energy (EPA-DOE) Interagency Agreement, EPA No. 79-D-X0533, DOE Contracts DE-AC05-7600R00242 and DE-AC06-76-RL0 1830 and U.S. Department of Agriculture Grant 79-CRSR-2-0485.

² Present address: Biology and Chemistry Department, Pacific Northwest Laboratory, Richland, WA 99352.

³ Present address: South Carolina Electric and Gas Company, Columbia, SC 29218.

⁴ Present address: Department of Veterinary Anatomy, College of Veterinary Medicine, College Station, TX 77843.

Manuscript received 16 January 1984.