No description available.

No description available.

No description available.

No description available.

No description available.

Peptide, plasma free, erythrocyte free and serum protein amino acid arteriovenous differences were quantified across the gastrointestinal tract (GIT) and liver of growing calves during a "steady state" and fasting metabolism. Six Holstein steer calves (136 kg) surgically equipped with cannulae in the aorta, portal vein and hepatic vein were maintained under constant light and fed a natural diet as 24 hourly meals per day. Blood was obtained simultaneously from all cannulae at 9 to 12 d postsurgery during the midpoint of a 1-hr feeding interval and following a 72-hr fast. Most amino acids were added to plasma by the GIT but fasting reduced the magnitude of this addition. GLN and GLU were the only plasma amino acids removed by the GIT. The liver removed a large portion of amino acids in portal plasma but a net splanchnic plasma free amino acid output occurred. Hepatic removal of amino acids, particularly VAL, ILE and LEU, increased after fasting. The GIT generally removed amino acids from the erythrocyte while the liver contributed amino acids to this pool. Peptide amino acids increased as blood crossed the GIT. Responses paralleled those of plasma free amino acids in direction but were threefold greater for peptide amino acids. A net output of peptide amino acids from the splanchnic bed was observed. Generally amino acids were added to the primarily globulin, albumin and mixed protein serum fractions while the pure albumin fraction contributed amino acids to the GIT. Fasting reversed the direction of response in the four fractions monitored. Arteriovenous differences for amino acids in two largely albumin fractions responded oppositely indicating a potential transport role of other proteins in these fractions. A more variable response was observed across the liver with direction and magnitude dependent upon individual amino acids. Fasting resulted in a release of amino acids by the liver into all four fractions. Several blood pools appear to be involved in the interorgan transport of amino acids. The extent and direction of transport varies with tissue, blood pool, nutritional status and amino acid. Quantitatively, peptides appear to be highly involved in interorgan movement of amino acids. / Ph. D.

Abstract not available

Postprandial urea production in subjects with insulin dependent diabetes mellitus (IDDM) on conventional insulin therapy is normal when the previous diet is high in protein, but there is an incomplete adaptive reduction in urea production following protein restriction. To evaluate the nutritional implications of restricted protein intake in human diabetes mellitus, it is first necessary to establish a reliable method to measure changes in urea production and amino acid catabolism in response to changes in dietary protein intake. We therefore tested (1) the accuracy of the urea production rate (Ra) to depict changes in urea production, (2) whether sulfate production can be accurately depicted using tracer or nontracer approaches, after establishing the use of electrospray tandem mass spectrometry to measure sulfate concentrations and 34SO4 enrichments following administration of the stable isotope tracer sodium [34S]sulfate, (3) the reproducibility of urea and sulfate measurements following a test meal low in protein (0.25 g/kg) in subjects previously adapted to high (1.5 g/kg.d) and low (0.3 g/kg.d) protein intakes, and compared the metabolic fate of [ 15N]alanine added to the test meal with that of [15N] Spirulina platensis, a 15N-labeled intact protein, and (4) whether we could identify the differences in postprandial urea and sulfate productions between normal subjects and persons with IDDM receiving conventional insulin therapy previously adapted to high protein intake, when the test meal was limiting in protein. Under basal conditions, steady state urea Ra is an accurate measure of urea production. Following changes in urea production, both the tracer and nontracer methods seriously underestimated total urea Ra. The tracer method overestimated sulfate production by 20%, but the nontracer method provided an accurate measure of sulfate production and, hence, sulfur amino acid catabolism. Postprandial changes in urea and sulfate productions following normal ada

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Amino acid absorption across rat intestine in vitro was inhibited or stimulated by insulin depending on the hormone serosal concentration. The absence of sodium ions from the incubating solution resulted in a significant decrease of L-alanine absorption. However, L-alanine was enhanced in a sodium-free medium by the addition of insulin on the serosal side of the intestine. A sizable decrease in L-alanine and L-lysine absorption was produced by introduction of D-glucose (0.2 % and 2 %) in the Krebs-Ringer's incubating buffer. Nevertheless, the presence of D-glucose did not prevent the stimulatory effect of insulin on amino acid absorption