Fatty acids and intestinal metabolism

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Abstract
The effect of different concentrations of saturated straight-chain C6[long dash]C20 fatty acids on rings of rat small intestine has been studied in vitro. At 0[center dot]6 m[image] the C7[long dash]C15 fatty acids inhibited respiration by more than 5% and the C12-C15 acids inhibited by more than 15%. At 6[center dot]0 m[image] the C6-C19 acids inhibited respiration by 14% or more and the C9[long dash]C13 acids inhibited by more than 60%. The oxidation of glucose (5 m[image]) by intestinal rings was inhibited by 0[center dot]6 m[image]- and 6[center dot]0 m[image]-fatty acids.The pattern of inhibition resembled the inhibition of respiration. The C9-C13 acids were the most potent, causing over 70% inhibition at 6[center dot]0 m[image]. The incorporation of glucose carbon into lipids was inhibited in a similar manner. Glucose concentrations up to 40 m[image] did not reverse the inhibition of respiration caused by 1[center dot]Om[image] -lauric acid. The uptake of glucose by intestinal rings in 10 min. was slightly stimulated (6%) by 0[center dot]4 m[image]-lauric acid, but was inhibited 13% by 2[center dot]5 m[image]-lauric acid. Both 10 m[image]-lauric acid and 7[center dot]78 m[image]-palmitic acid prevented the accumulation of glucose against a concentration gradient in the fluid bathing the serosal surface of intestinal sacs. The formation of lactic acid was stimulated by 0[center dot]4 m[image]-and 2[center dot]5 m[image]-lauric acid by 27 and 41% respectively after 10 min. the loss of lactic acid from the tissues was stimulated by 2-5 m[image]-lauric acid. The inhibition of respiration by lauric acid appeared at a concentration of 0[center dot]01 m[image] and increased as the concentration was raised to 10 m[image]. At 10 m[image] the inhibition was 36% of that in the absence of fatty acids. In the presence of succinic acid or glutamic acid, 1[center dot]0 m[image]-lauric acid inhibited the respiration of intestinal rings by 29%. The oxidation of the glutamic acid to CO2 was inhibited by 63%.