A CRANIAL MESENTERIC VEIN PREPARATION FOR MEASUREMENT OF AMINO-ACID-UPTAKE BY LAMBS

A surgical preparation was developed to measure uptake of amino acids from the small intestine into the cranial mesenteric vein (CMV) of lam bs. Results from this preparation were compared with those from the tr aditional hepatic portal vein (PV) preparation in the same lambs. Necr opsy revealed that, in contrast to the PV preparation which included a ll portal-drained viscera, the CMV preparation drained primarily small intestine (0.84-0.92 small intestinal mass). The CMV preparation cont ributed 0.238 of blood flow from and 0.307 of oxygen consumption by th e PV preparation. Venous-arterial differences for alpha-amino nitrogen (AAN), phenylalanine (Phe) and tyrosine (Tyr) were three- to fourfold greater in the CMV than in the PV preparation, indicating that the CM V preparation is more sensitive for measuring amino acid uptake. The r atio CMV/PV for uptake of AAN was 0.61 (P < 0.001), but this ratio was much closer to unity (mean 0.84) for Phe and Tyr. Since the CMV prepa ration drains primarily the small intestine, through which all amino a cid absorption occurs, it should prove to be extremely valuable for st udying absorption from and metabolism within this organ using a combin ation of arteriovenous and isotopic tracer techniques.