title: Comparison of 59Fe3+ uptake in vitro and in vivo by mouse duodenum.
abstract: Initial rates of 59Fe3+ uptake by mouse duodenal fragments (in vitro) and tied-off duodenal segments (in vivo) have been characterised for control and hypoxic animals. 59Fe3+ uptake by duodenal fragments was rapid, selective and dependent on medium Fe3+-nitrilotriacetate concentration. Most of the 59Fe3+ uptake (70-75%) occurred via the mucosal route and was dependent on the metabolic state of the tissue. Mucosal uptake showed an adaptive increase following exposure of animals to 3 days hypoxia; the enhancement was due to a 2-3-fold increase in Vmax app, without any significant changes in the Km app. Studies of upper small intestine transit times showed a mean residence time of 4-5 min for 59Fe-labelled mouse chow, emphasising the importance of initial uptake measurements. Time courses for in vivo total mucosal uptake exhibited linearity over a wide variety of absorption rates after correction for the permeation by intact metal-chelate complex. The corrected uptake showed a hyperbolic dependence on medium Fe3+-nitrilotriacetate concentration. Kinetic studies revealed a 2-3-fold increase in total mucosal uptake in hypoxia. Mucosa-to-carcass transfer of 59Fe was also markedly increased by chronic hypoxia. The in vitro system exhibits similar qualitative and quantitative kinetics for Fe3+ transport via the mucosal membrane to those obtained in vivo. The results observed in vitro are thus valid and provide a convenient method for further studies on Fe3+ transport in animals and in man.
mesh_terms: D000818:Animals; D002860:Chromium Radioisotopes; D003037:Cobalt Radioisotopes; D004386:Duodenum / Q000378:metabolism*; D004492:Edetic Acid / Q000378:metabolism; D004734:Energy Metabolism; D000860:Hypoxia / Q000378:metabolism; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007504:Iron Radioisotopes; D007700:Kinetics; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D009571:Nitrilotriacetic Acid / Q000378:metabolism; D014805:Vitamin B 12 / Q000378:metabolism
chemical_list: D002860:Chromium Radioisotopes; D003037:Cobalt Radioisotopes; D007504:Iron Radioisotopes; D004492:Edetic Acid; D007501:Iron; D009571:Nitrilotriacetic Acid; D014805:Vitamin B 12