Effect of intake on whole body plasma amino acid kinetics in sheep (original) (raw)
Related papers
Blood cell to plasma gradients of amino acids in arterial and venous blood in fed and fasted rats
Comparative biochemistry and physiology. Comparative physiology, 1994
Measurement of amino acid concentrations in blood cells and plasma, and the calculated blood cell to plasma gradients (C/P) from both afferent and efferent vessels to tissues, allowed evaluation of the effect of several tissues (splanchnic bed, skeletal muscle and kidney) on blood amino acid distribution in fed and starved rats. Combined effects of tissues and erythrocyte transport capabilities determined specific C/P values for each amino acid. For amino acids related to the L-system, the high capacity of this erythrocyte transport many buffer some C/P changes as an effect of tissue metabolism. For less permeable amino acids (like Asp and Glu) plasma changes were mainly responsible for changes in C/P values, whereas for other amino acids (such as basic amino acids) blood cells became the main determinants of C/P changes, mainly in starvation. In general, the role of erythrocytes in amino acid transport was enhanced in starvation.
British Journal of Nutrition, 2001
Under conditions of chronic supply the liver removes most amino acids (AA) in excess of net anabolic needs. Little information is available, however, on how acute alterations in AA supply (as might occur with once-daily feeding regimens) are controlled by the liver. Are these also extracted completely in a ‘first-pass’ manner or are there limitations to hepatic uptake? Furthermore, is the rate of removal ‘saturable’ (by Michaelis–Menten kinetics) over the range of supply experienced under normal feeding conditions? These questions have been addressed in a study that involved acute (4.5 h) increases in AA supply. Four sheep were prepared with trans-hepatic vascular catheters and were offered a basal diet (equivalent to 1.6×energy maintenance) throughout. On four occasions, at 7 d intervals, they were infused with various amounts of an AA mixture into the mesenteric vein over a 4.5 h period. The mixture contained fourteen AA in the proportions present in rumen microbial protein. The a...
British Journal of Nutrition, 2023
This study evaluated the importance of a correction for amino acids (AA) released into the hindgut on a measure of AA absorption kinetics and tested whether AA absorption kinetics are related to the extent of AA absorption using the growing pig as a model for humans. Thirty-six nineweek-old pigs (22•3 kg) received a diet containing whey protein as the sole protein source for 8 d. Pigs received their last meal containing the indigestible marker titanium dioxide before being euthanised at 1, 2, 3, 4, 6 and 12 h post-feeding. The entire content of each gastrointestinal tract (GIT) region was collected to determine AA released into the hindgut, and the kinetics and extent of AA absorption (uncorrected and corrected for AA entering the hindgut). Amounts of AA released into the hindgut increased over time (e.g. 33 and 180 mg of Glu for 4 and 6 h post-feeding). The corrected apparent amount of each AA absorbed from the GIT lumen after 4 h post-feeding was generally lower (P ≤ 0•05) than the uncorrected counterpart. Differences in both the kinetics and extent of AA absorption were observed across AA. For example, the time to reach half of the apparent AA absorption (T50) was 1•5 and 3•4 h for Met and Arg, respectively, whereas their extent of apparent absorption was 93 and 73 %. Negative correlations between parameters related to kinetics and the extent of apparent absorption were observed (e.g. for T50 r = −0•81; P < 0•001). The kinetics of AA absorption is related to the extent of AA absorption.
British Journal of Nutrition, 2001
Both plasma and red blood cells contain amino acids (AA), but the relative amount of AA transferred from each vascular compartment to the tissues remains unclear. For splanchnic tissues, the relative transfers between the plasma, the red blood cells and the tissues may vary with nutritional state, but whether the same situation pertains for other tissues is not known. The current study focused on the transfer of lysine from plasma and red blood cells across the hindquarters of sheep offered four levels of intakes (0.5, 1.0, 1.5 and 2.5×maintenance energy). This design, coupled with use of [U-13C]lysine as tracer, also allowed the effect of intake on protein kinetics to be examined. At all intakes, the concentration of lysine in the sheep’ red blood cells exceeded that in plasma by 50 % (P<0.001), while the distribution of labelled lysine between the plasma and the red blood cells was 0.71:0.29. Net lysine uptake by the hindquarters increased in a linear manner (P<0.001) with i...
The British journal of nutrition, 1997
The hepatic responses of late gestation, dry dairy cows to acute (6 h) infusions of an amino acid (AA) mixture (Synthamin; 0.0, 1.1, 2.2, 4.4, 8.8 and 17.6mmoVmin) into the mesenteric vein were determined. Neither blood flow nor 0 2 consumption across the portal-drained viscera (PDV) and liver was significantly altered by infusion. Similarly, there were no effects on net absorption, or hepatic removal, of acetate, propionate, butyrate or NH3. Glucose PDV appearance was unchanged but hepatic glucose production increased (P = 0.032) by 0.2 mmoVmin per mmoVmin of AA infused.
Absorption and Transportation of Amino acids in animals : A Review
2017
Small peptides (primarily di-and tri-peptides) and amino acids are absorbed from the small intestine. Ileum and jejunum are the more active sites of amino acid absorption. Both peptide and amino acids can be absorbed against a concentration gradient and require energy in the form of ATP. The energy dependent transport of amino acids is linked with co-transport of Na + , while in case of peptides it is linked with co-transport of protons (H +). Animal's needs of the for body growth and maintenance is fulfilled by free amino acids and peptides. Although both are absorbed from the gastrointestinal tract, however, absoprtion of peptides occurs at much rate as compared to free amino acids. In ruminants peptides are more important form of amino acid than free amino acids, and major sites of peptide absorption includes rumen and omasum. Ruminal microorganisms potentially are vital in regulating the composition of peptides offered for absorption. These observations will have major effect on understanding the processes of digestion and absorption of proteins in ruminants. Furthermore, these observations will dramatically alter many strategies used in providing for the proper protein nutrition of ruminants.
Influence of leucine infusion on intracellular amino acids in humans
European Journal of Clinical Investigation, 2008
A continuous intravenous infusion of Lleucine (300 pmol min-') was given to 12 healthy females over a 2; h period. Arterial plasma concentrations of amino acids and the keto acids of the branched-chain amino acids (BCAA) were measured. In six subjects muscle biopsies were taken before and at the end of the infusion for determination of intracellular (i.c.) free amino acid concentrations, and leg exchange of amino acids was measured. During infusion the plasma level of leucine rose sixfold. Approximately 40% of the infused amount was taken up by muscle. Of this, half was accumulated intracellularly, where the free leucine concentration increased from basal 190k22to580f 1 lOpmolI-'ICW(intracellular water) at the end of infusion. The concentrations of most other amino acids, above all the other BCAA and the aromatic amino acids, decreased, by 17-48'X) in the i.c. pool and by 17-79'K) in plasma. The plasma level of ketoisocaproic acid (KIC), the keto acid of leucine, increased in parallel with that of leucine. The concentration of keto valine, ketoisovaleric acid (KIV), decreased by 75%, whereas the keto acid of isoleucine, ketomethylvaleric acid (KMV), was unchanged. Leg release of alanine decreased significantly, whereas the exchange of other amino acids were unchanged. Taken together, decreased i.c. and plasma concentrations but unchanged leg exchange of tyrosine and phenylalanine suggest i.c. accumulation of protein. It can be calculated that approximately 40% of the leucine taken up by muscle was accumulated in the intracellular free pool, some 20% could have been incorporated into protein and 40% was probably oxidized.
British Journal of Nutrition, 1992
In ten lambs (average live weight 33 kg), five offered 300 g/d (approximately 0 6 x maintenance; L) and five 900 g/d (1.8 x maintenance; H), tissue protein synthesis was measured by three procedures simultaneously. The techniques involved continuous infusion of [U-14Clphenylalanine and [ l-13C]leucine over 7-8 h followed by a terminal large dose of 115Nlphenylalanine during the last 30 or 60 min. Rates of protein synthesis were then calculated based on the free amino acid or 0x0-acid isotopic activity in either arterial, iliac venous blood or tissue homogenate for the continuous-infusion studies, or on plasma or tissue homogenate for the large-dose procedure. For muscle ( > 99 YO), and to a lesser extent skin (85-93 YO), effective flood conditions were achieved with the (''N]phenylalanine but were either not established or maintained for liver and tissues of the gastrointestinal tract (< 50 YO). The large dose of phenylalanine also caused changes in the concentration and isotopic activity of blood leucine and 4-methyl-2-0x0-pentanoate. Based on the assumption that the large-dose procedure yields the closest value for the true rate of protein synthesis (L 1.97 %/d, H 2.85 %/d) then, for muscle, only values based on the homogenate as precursor gave comparable results for both leucine (L 1.83 %Id, H 3.01 %/d) and phenylalanine (L 1.67 %/d, H 2.71 %/d) continuous infusion. The values based on the arterial or venous amino or 0x0-acid were significantly less, more so at the lower intake. In contrast, for skin, a tissue dominated by export protein synthesis, values from the large-dose procedure (L 6.37 %/d, H 10.98 %Id) were similar to those derived with arterial or venous metabolites as precursor (L 5.23 and 693%/d, H 9.98 and 11.71 %/d for leucine), but much less than those based on homogenate data. Based on the large-dose technique, protein synthesis increased with intake in muscle (P < 0.001), skin (P = 0.009) and liver (26.7 v. 30.5 %/d; P = 0.029). The contributions of muscle and skin to total protein synthesis were approximately equal. The incremental efficiency of conversion for muscle of synthesized protein into deposition appeared to be similar to values reported for rodents.
British Journal of Nutrition, 2001
It has been suggested that protein synthesis in peripheral tissues: (1) responds in a curvilinear manner to increasing feed intake over a wide range of feeding levels; and (2) has a greater sensitivity to intake than protein breakdown. The aim of the present experiment was to test these hypotheses across the ovine hindlimb. Six growing sheep (6–8 months, 30–35 kg), with catheters in the aorta (two), posterior vena cava and jugular vein, received each of four intakes of dried grass pellets (0·5, 1·0, 1·5 and 2·5×maintenance energy; M) for a minimum of 7 d. A U-13C-labelled algal hydrolysate was infused intravenously for 10 h and from 3–9 hpara-aminohippuric acid was infused to measure plasma flow. Arterial and venous plasma were obtained over the last 4 h and the concentrations and enrichments of thirteen13C-labelled amino acids (AA) were determined by GC–MS. As intake increased, a positive linear response was found for plasma flow, arterial concentrations of the aromatic and branche...
Amino acid metabolism in the piglet
British Journal of Nutrition, 1976
1. Supplementing a lysine-deficient diet (5 g lysine/kg) with five increments of lysine, each of 2 g/kg, resulted in increases in growth rate of Yorkshire piglets, aged between 3 and 7 weeks, up to the highest level of lysine (15 g/kg).2. The free lysine concentration of plasma tended to increase as the dietary lysine level increased from 13 to 15 g/kg, and plasma threonine concentration decreased significantly as the lysine content of the diet was increased from 11 to 15 g/kg indicating that threonine was the second limiting amino acid in the diet.3. Oxygen consumption and carbon dioxide production of the piglets were not influenced by supplementing the diets with lysine. The heat production was 0.313 kJ/min per kg body-weight in the 6 h experimental period.4. Supplementation of the diet with lysine had no consistent effect on the recovery of 14C as 14CO2 from a single dose of l-[U-14C]lysine.5. Adjustment of the determined recoveries of the tracer dose of lysine for the difference...