Timing and route of exposure affects crystal formation in melamine and cyanuric exposed male and female rats: Gavage vs. feeding |
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Authors: | Robert L Sprando Renate Reimschuessel Cynthia B Stine Thomas Black Nicholas Olejnik Michael Scott Zachary Keltner Omari Bandele Martine Ferguson Sarah M Nemser Andriy Tkachenko Eric Evans Tina Crosby Kellie Woodling Lucie Loukotková Gonçalo Gamboa da Costa |
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Institution: | 1. Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD 20708, United States;2. Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD 20708, United States;3. National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, United States |
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Abstract: | Effects of the dosing matrix and timing on the onset of renal crystal formation were evaluated in male and non-pregnant female rats (Fisher 344) exposed to both melamine (MEL) and cyanuric acid (CYA) for 28 days. Rats were fed ground feed containing 60 ppm MEL and 60 ppm CYA, (5 mg/kg bw/day equivalent), or exposed via oral gavage to carboxymethylcellulose containing 5 mg/kg bw MEL followed by 5 mg/kg bw CYA either consecutively (<1 min apart) or delayed 45 min after MEL. Staggered gavage exposure to MEL/CYA caused extensive renal crystal formation as compared to when the two compounds were administered consecutively or in feed. Treatment related effects included reduced weight gain, feed consumption, and testicular weight and increased kidney weight, water consumption and urine output. Animals from the staggered MEL/CYA gavage exposure group became ill and were removed after 9 days of exposure. Approximately 1 week after the initiation of exposure microscopic urinalysis revealed MEL/CYA crystals in both groups of gavaged animals but not in the MEL/CYA feed treatment groups. Urinary crystals were smaller (10 μm) in animals consecutively gavaged. In contrast the urinary crystals were larger (20–40 μm) and frequently clumped in the animals in the staggered gavage group. |
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Keywords: | CEG consecutive exposure group CYA CYA FC feed control FEG feed exposure group GC gavage control MEL melamine SEG staggered exposure group |
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