KINETIC-ANALYSIS OF THE INTESTINAL IRON-ABSORPTION PROCESS IN-SITU - THE POTENTIAL OF VASCULARLY AUTOPERFUSED INTESTINAL LOOPS

1 Blood sampling from mesenteric venules during absorption in situ is a useful tool to analyse intestinal absorption kinetics and prehepatic metabolism in different sections of the rat small intestine. By use o f a micromanipulator, the method can be applied to the duodenum. This part of the small intestine shows the strongest adaptation of non-haem iron absorption to the demand for iron.2 Iron absorption kinetics was linear in duodenal and jejunal segments. In iron-deficient animals, i ntestinal iron absorption capacity was increased in the duodenum, whil e simultaneously determined galactose absorption showed no change. 3 I n situ perfusion and cannulation of mesenteric venules in duodenal seg ments are described. The use of a micromanipulator permits varying the blood volume collected by changing the vertical angle between the can nula and the mesenteric vessel. 4 Intestinal iron absorption rates rem ained close to constant when blood now rates were varied by a factor o f about ten. Plasma concentrations of absorbed iron vs mesenteric bloo d flow rates followed a hyperbolic function, as the plasma concentrati on of absorbed iron in mesenteric venules increased to the same extent as the blood flow decreased. 5 As the plasma transferrin concentratio n did not change over the experimental period, the concentration of ab sorbed iron in the mesenteric plasma exceeded the iron-binding capacit y of plasma transferrin at low blood flow rates. This observation show s that enhancement of intestinal iron absorption does not require a co rresponding increase in plasma iron-binding capacity in the intestinal tissue. 6 Vascularly perfused gut loops were also used to measure pre hepatic metabolism, which may influence organotropism of carcinogenic metabolites. Therefore, this type of preparation is likely to find a v ariety of toxicological applications.