Localization of lipid reesterifying enzymes of the rat small intestine effects of jejunal removal on ileal enzyme activities

Abstract

1. 1. The difference between proximal and distal small bowel regarding lipid absorption was studied. Uptake and esterification of [1- 14C]oleic acid by everted sacs from the jejunum and terminal ileum were determined. Assays were also done for two of the lipid reesterifying enzymes at the various levels of the small bowel. Fatty acid-CoA ligase was determined spectrophotometrically by employing hydroxylamine which assays thioester bonds. Acyl-CoA: monoglyceride acyltransferase was determined by continuous recording spectro photometry using 5,5'-dithiobis-(2-nitrobenzoic acid) which reacts with sulfhydryl groups on liberated CoA. 2. 2. Uptake and esterification of [ 1–14C] oleic acid was greater in sacs prepared from the proximal compared to the distal small bowel. Activities for fatty acid-CoA ligase and acyl-CoA: monoglyceride acyltransferase were significantly greater in the proximal small bowel. 3. 3. An attempt to induce greater enzyme activities in the ileum was done by surgically removing or bypassing the jejunum. Enzyme activities were elevated in the ileum in experimental rats compared to controls when assays were done 1 month af ter sargey. Total enzyme activities were more increased compared to the specific activities because of the hypertrophic effects produced in the remaining ileum following removal of the jejunum. 4. 4. These findings support the concept that the proximal small bowel is the major site of lipid absorption under normal conditions but that the ileum has the potential to absorb lipid if the jejunum is removed.