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 of 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, intestinal iron absorption capacity was increased in the duodenum, while simultaneously determined galactose absorption showed no change. 3 In situ perfusion and cannulation of mesenteric venules in duodenal segments are described. The use of a micromanipulator permits varying the blood volume collected by changing the vertical angle between the cannula and the mesenteric vessel. 4 Intestinal iron absorption rates remained close to constant when blood flow rates were varied by a factor of about ten. Plasma concentrations of absorbed iron vs mesenteric blood flow rates followed a hyperbolic function, as the plasma concentration of absorbed iron in mesenteric venules increased to the same extent as the blood flow decreased. 5 As the plasma transferrin concentration did not change over the experimental period, the concentration of absorbed iron in the mesenteric plasma exceeded the iron-binding capacity of plasma transferrin at low blood flow rates. This observation shows that enhancement of intestinal iron absorption does not require a corresponding increase in plasma iron-binding capacity in the intestinal tissue. 6 Vascularly perfused gut loops were also used to measure prehepatic metabolism, which may influence organotropism of carcinogenic metabolites. Therefore, this type of preparation is likely to find a variety of toxicological applications.
Hunder
G
G
Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universtität, München.
Osterloh
K
K
Schümann
K
K
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D007501:Iron / Q000493:pharmacokinetics*; D000090463:Iron Deficiencies; D008643:Mesentery / Q000098:blood supply; D011485:Protein Binding; D051381:Rats; D014168:Transferrin / Q000378:metabolism
D014168:Transferrin; D007501:Iron