FLUORIDE ABSORPTION FROM DISODIUM AND CALCIUM MONOFLUOROPHOSPHATES FROM THE GASTROINTESTINAL-TRACT OF RATS

The contribution of the stomach and the small intestine to the in vivo absorption of fluoride from disodium and calcium monofluorophosphates was studied in comparison with that observed when sodium fluoride is given to rats. In vitroexperiments with ligated duodena were also carr ied out. Fasted rats were given orally 50 mug of fluoride in pH 6.3 bu ffered disodium monofluorophosphate solutions with and without 50 mM a dded calcium. The same amount of fluoride was administered in the form of an aqueous sodium fluoride solution. In both cases the fluoride so lutions contained trace amounts of (C-14)-labeled polyethyleneglycol a s a marker for the study of water movement through the gastrointestina l tract. Results obtained show the small intestine as the main site of the absorption of the studied compounds. Under the fasting conditions employed in our study gastric absorption was in turn,almost negligibl e. While fluoride transport from sodium fluoride seems to occur throug h a difussion mechanism, disodium and calcium monofluorophosphates app ear to be absorbed through a more complex mechanism involving an enzym atic hydrolysis and an independent and possibly parallel direct tissue absorption of a soluble, neutral calcium monofluorophosphate complex.