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Department of Oral Sciences, University of Minnesota, Minneapolis, MN 55455
The contribution of the stomach and the small intestine to absorption of fluoride from the gastrointestinal tract was examined in rats. Fasted adult male rats weighing
350 g were given 50 µg of fluoride in 1 ml of water by stomach intubation, with 14C-labeled polyethylene glycol as a marker of water movement through the gastrointestinal tract. Rats were killed at intervals up to 120 min, and the stomach, duodenum, jejunum, ileum, distal ileum and cecum were rapidly clamped and removed for fluoride analysis and 14C counting. Approximately 90% of the fluoride dose was absorbed in 120 min. Peak plasma fluoride concentration occurred 10 min after intubation and began to decline after 40 min as the rate of fluoride absorption slowed. Absorption from the stomach was derived from rates of gastric emptying and remaining fluoride. Even at 10 min after intubation, when the bulk of the fluoride remained in the stomach, only approximately 25% of fluoride absorption had occurred from the stomach and 75% from the small intestine. After 120 min, 19.8% of total fluoride absorption had occurred from the stomach. Although the stomach is unquestionably a significant site for fluoride absorption, its contribution is much smaller than that of the small intestine.
KEY WORDS: fluoride gastrointestinal absorption male rats
1 Supported by grant #DE 08766 from the National Institute for Dental Research, Bethesda, MD.
2 To whom reprint requests should be addressed.
3 Mineral Resources Research Center, University of Minnesota, Minneapolis, MN.
Manuscript received 13 December 1988. Revision accepted 2 June 1989.
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