The Failure of Absorption of DC Silicone Fluid 703 from the Gastrointestinal Tract of Rats

Abstract

The intestinal absorption of silicone fluid 703, a methyl phenyl polysiloxane, has been studied in the rat. This silicone was chosen for the present investigation because of its lipid-like character and its solubility in olive oil.The experimental findings demonstrate that very little, if any, silicone is absorbed when fed in olive oil. No silicone was found in the lymph lipids of cannulated rats fed the silicone, and balance experiments by recovery of the organosilicon compound and triglyceride after feeding to rats for three hours showed that 85 % of silicone fluid 703 was recovered from the gastrointestinal tract, whereas 70% of the fed triglyceride was absorbed. The unabsorbed silicone was concentrated chiefly in the intestinal lumen. Balance experiments by recovery of the organosilicon compound after long-term feeding gave recoveries of 96% of the silicone. This amount was recovered entirely from the lower part of the gastrointestinal tract and the faeces. No silicon fluid 703 was found in the liver, kidneys, or fat depots. The urine contained no soluble silica.The increasing use of various silicones for lubricating baking pans and surgical appliances, as antifoaming agents in the manufacture of sugar, beverages, wine, chewing-gum base, drugs, and cosmetics have led several workers (Rowe, Spencer, and Bass, 1948;Kern, Anderson, and Harris, 1949;Largett, Blackstone, and Roth, 1950;Child, Paquin, and Deichmann, 1951; Cutting, 1952) to study the toxicity of this class of compounds. Most of the experimental work has been the feeding of DC silicone fluids 200 and 555 and DC antifoam A.In all cases the silicones do not exhibit any significantly harmful effects in the rat and dog. These findings were based on long-term feeding experiments of the silicones to experimental animals followed by gross and microscopic examinations of the more important organs of the animals together with examination of the stool, urine, and blood in some cases.It is possible in the interpretation of the earlier results that no significant toxic effects were produced because of the lack of absorption of the silicones from the intestines and that their elimination may be too rapid to cause any toxic effects to become evident. Indeed, Drill (1954) reported that when dogs were fed high doses of "DC antifoam A" the silicone was recovered quantitatively from the stool.The investigation reported here is a study of the absorption of DC silicone fluid 703, a methylphenyl polysiloxane, from the gastrointestinal tract of rats.There is experimental evidence that some lipidlike materials other than triglyceride fats are rapidly absorbed from the gastrointestinal tract when they are fed dissolved in a triglyceride vehicle (Bloom, Chaikoff, Reinhardt, Entenman, and Dauben, 1950;Daniel, Frazer, French, and Sammons, 1951;Borgstrom, 1951;Kim and Ivy, 1952). Absorption may not occur when they are fed alone (Ahmad, 1931; Cook, 1936 (Parr, 1908(Parr, , 1919, followed by estimation of the soluble silicate by the formation of molybdenum blue (Foulger, 1927)...

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