Uptake and compartmental distribution of fatty acid by rat small intestine in vivo

The uptake and esterification of micellar [3-H]oleate and [14-C] palmitate were uniform along the entire length of the small intestine in vivo. Fatty acids (FA) radioactivity taken up by the small intestine could be described in terms of four functionally distinct compartments analogous to those described in vitro. The KRP-extractable compartment (KEC) and albumin-extractable compartment (AEC) contained reversibly adherent unesterified FA radioactivity, while the tissue free and esterified FA compartments contained irreversibly bound radioactivity. Wheras 27% and 63% of FA uptake were reversibly bound in the KEC and AEC by the most proximal and most distal regions of the small intestine in vitro (15), less than 10% was contained in these compartments in vivo, independent of location. Linear inverse relationships were found betweeen tissue FA esterification and proportion of FA radioactivity present in the KEC,AEC, and the tissue free FA compartment in vivo. These observations allow for the possibility that FA molecules pass through these compartments prior to esterification.