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https://hdl.handle.net/2142/71309
Description
Title
Acute Selenium Toxicosis in Sheep
Author(s)
Blodgett, Dennis Jay
Issue Date
1983
Department of Study
Veterinary Medical Science
Discipline
Veterinary Medical Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Veterinary Science
Abstract
The toxicity, toxicokinetics, and progressive pathological changes produced by sodium selenite in sheep following parenteral administration were evaluated.
In the intramuscular study, the LD(,50) for sodium selenite was 0.7 mg selenium/kg body weight with a standard error of 0.035 over a 192 hour observation period. The most evident clinical signs were dyspnea and depression. At necropsy, the most consistent lesions were edematous lungs and pale mottled hearts. Highest tissue selenium concentrations in declining order were found in the liver, kidney, and heart. The blood selenium disappearance curves were triphasic for those animals which lived for at least 36 hours after selenium was administered, whereas animals which died within 36 hours after selenium administration had biphasic disappearance curves. The (alpha) rate constants of selenium disposition exhibited a dose dependency; so that for animals which received 0.4, 0.6, 0.7, and 0.8 mg selenium/kg body weight, the (alpha) rate constants were 0.1098, 0.0786, 0.0458, and 0.0339 hr.('-1), respectively. The mean (beta) elimination rate of the 11 sheep which exhibited triphasic toxicokinetics was 0.0011 hr.('-1) which represented a biological half-life of 630 hours (26.25 days).
Four sheep injected intravenously with 0.7 mg selenium/kg body weight survived the 192 hour post-injection observation period. Semilogarithmic plots of blood selenium concentration versus time were triphasic. The (alpha) and (beta) rate constants of sheep administered a single dose of selenium intravenously were significantly greater than those obtained when sheep were injected intramuscularly with 0.7 mg selenium/kg body weight.
In the continuous intravenous infusion study, a gradient of tissue selenium concentrations was attained with 4, 8, and 12 hour infusions at steady state concentrations of 2500, 3000, and 3500 ppb selenium in the blood. The heart was the target organ of acute selenium toxicosis. A dose-response relationship was observed in the heart with degeneration evident in all hearts and necrosis present in the 2 hearts with the highest concentrations of selenium.
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