Resistance of intestinal triglyceride transport capacity in the rat to adaptation to altered luminal environment

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Abstract
Previous studies have shown that the transmucosal transport capacity for triolein is slower in distal compared with proximal regions of rat small intestine. The effect of altered luminal conditions on the relative capacities for [14C]triolein transport through different regions of intestinal wall were examined by determining the net accumulation of 14C-lipid in the mucosa during maximal steady [14C]triolein absorption. The high 14C-lipid accumulation in distal mucosa was not reduced after direct distal infusion of oleic acid and monolein for 7 days before challenge (substrate induction). No decrease in distal intestinal lipid accumulation was found 1 month after removal of the proximal 40% of intestine beyond the duodenum. Conversely, alteration of the luminal environment in the proximal intestine by 3 days of starvation or by ileal resection did not increase the tissue 14C-lipid concentration in this region during maximal [14C]triolein challenge. When proximal and distal segments were exchanged without reduction in intestinal length, by jejunoileal transposition, major 14C-lipid accumulation still occurred in originally distal segments during 3 hr of [14C]triolein infusion 1 month later. Mucosal synthesis of triglyceride was equally efficient in jejunum and ileum, suggesting that the intrinsic differences in proximal and distal lipid accumulation during maximal rate transport were related to a relatively limited capacity for chylomicron synthesis or secretion in the distal intestine.

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