Uptake of bismuth in motor neurons of mice after single oral doses of bismuth compounds

Bismuth, a component of many gastrointestinal medications, is a heavy metal little studied as regards nervous system uptake. We were interested to see if low doses of intragastric bismuth entered the nervous system, and if di etary selenium influenced the amount of bismuth detected. Mice were given 4 0 to 1200 mg/kg of bismuth subnitrate (BSN), bismuth subsalicylate (BSS), c olloidal bismuth subcitrate (CBS), or ranitidine bismuth citrate (RBC) intr agastrically. Mice on low- or high-selenium diets were given 4 to 32 mg/kg of bismuth from RBC. One week later, sections of nervous tissue were staine d with autometallography to detect bismuth grains (Bi-AMG). Bismuth was fou nd in neurons with axons outside of the nervous system, in particular motor neurons, and in cells outside the blood-brain barrier. The lowest bismuth dose which resulted in Bi-AMG in motor neurons was 696 mg/kg from BSN, 57 m g/kg from BSS, 29 mg/kg from CBS, and 26 mg/kg from RBC. No bismuth was see n in motor neurons of mice on the low-selenium diet. Intragastric doses of bismuth therefore enter mouse motor neurons, and the amount detectable vari es with dietary selenium. (C) 2000 Elsevier Science Inc. All rights reserve d.