Influence of Sodium Chloride and Certain Other Food Components on Fluoride Absorption in the Rat

Abstract

The effect of sodium chloride, wheat flour and some other food components on the intestinal absorption and skeletal storage of 18F-labeled fluoride (F) was investigated in the rat, with a view to the possible use of staple foods instead of drinking water for the caries-preventive administration of F. The main parts of the experiments were carried out as 4-hour tests following tube ingestion of 8 ml of water or food slurry containing 4 ppm F as 18F-labeled NaF. Femoral uptake of F was greater after ingestion of flour or egg yolk than after water. Addition of 350 mM NaCl reduced femoral F uptake from water and flour slurry but not from egg yolk. Egg white did not differ significantly from water. Individual variations were, as always, greater regarding intestinal absorption than femoral accumulation of F. The greater femoral uptake of F given with egg yolk (with or without NaCl), despite the large unabsorbed rest, was not explained by experiments with any of the egg yolk components, glutamic acid, aspartic acid, lecithin, lysine, cholesterol, orthophosphate or fat. Lysine reduced femoral uptake of F whereas fat (olive oil) had no effect. Rats given a calcium phosphate-rich diet prior to the ingestion of F retained more in the intestine and less in the skeleton provided F was ingested with water only, but not if the ingested volume was made viscous with carboxymethyl cellulose (CMC). The CMC increased the 4-hour femoral fixation of F about as much as flour, pure starch and egg yolk, and CMC gave an unchanged femoral F uptake after 1 hour despite delayed intestinal absorption. Skeletal fixation of parenterally administered F was not measurably influenced by the simultaneous ingestion of egg yolk, olive oil or cholesterol. With only 1 hour survival time after ingestion, sodium chloride produced a notably strong reduction of skeletal F uptake from both water and flour.