Intestinal passage of microencapsulated fish oil in rats following oral administration

Fish oil labelled with [(14)C-linolenin] tracer was orally administered by gavage as an oil-water mixture (free oil) or as an oil-in-water emulsion formulation (microencapsulated oil) to fasted rats. Groups of rats were then given food after gavage or alternatively not fed to examine the effect of food on intestinal passage. Feeding after gavage drives lumenal free oil faster through the gastrointestinal (GI) tract. Microencapsulation slows down the lumenal progression in the GI tract with feeding. Non-feeding also slows down the lumenal progress of free oil in the GI tract but this is not influenced by microencapsulation. Analysis of the relative distribution of the label along the GI tract tissue wall showed that the upper small intestine was the main site of label accumulation in the GI tract. Of the oil that remained in the lumen, there was slight protection against early uptake and metabolism in the stomach and upper GI tract in rats that were either fed or not fed after dosing when microencapsulated oil was administered. Microencapsulation increased the levels of radiolabel in the liver and blood. The primary organ for accumulation of radiolabel for both free and microencapsulated oils in rats that were fed or fasted after dosing was the liver.