Effect of intake on whole body plasma amino acid kinetics in sheep

While both the quantity and quality of food ingested are potent regulators of whole body protein metabolism in ruminants, little data are available on responses across a wide range of intakes. The current study examined the responses in whole body protein flux (PrF) to such intake changes and compared these with the responses across the hind-quarters (in a companion study). Six growing sheep (6-8 months, 30-35 kg) received each of four intakes of dried grass pellets (0.5, 1.0, 1.5 and 2.5 times maintenance energy; M) for a minimum of 7 days. At each intake, a mixture of U-13C amino-acids (AA) was infused intravenously for 10 h. Arterial plasma and blood were obtained over the last 4 h of infusion and the concentrations and the enrichments of thirteen 13C labelled AA were determined. The absolute values for plasma Irreversible Loss Rate (ILR) but also converted PrF varied between the AA. PrF values were lower for histidine, methionine, aspartate, glycine and proline (range 68 to 174 g x d(-1) at 1.5 M) than for isoleucine, leucine, valine and glutamate (range 275 to 400 g x d(-1) at 1.5 M). These discrepancies may be explained by (1) the differential AA removal by the splanchnic tissues, (2) the de novo synthesis of the non-essential AA, (3) the transfer of AA from the erythrocytes or plasma to the tissues. The first two assumptions require further investigation whereas recent work has shown a minor role for AA transfers between erythrocytes and tissues. For most AA, ILR and PrF responded linearly to intake but curvilinear responses were observed for phenylalanine, lysine, leucine, isoleucine and tyrosine. These differences were not due to hind-quarter metabolism and may involve the digestive tract and liver.     

Comparison of the effect of semisynthetic human insulin and porcine insulin on glucose kinetics, plasma free fatty acid and amino acid levels in man

The effect of semisynthetic human insulin on hepatic glucose output, peripheral glucose clearance, plasma levels of C-Peptide, free fatty acids and amino acids was compared with purified pork insulin using the glucose clamp technique. 8 normal overnight-fasted subjects received intravenous infusions of either human or porcine insulin at 20 mU/m2.min(-1) during 120 min achieving plasma insulin levels of approximately equal to 50 mU/l. Plasma glucose levels were maintained at euglycaemia by variable rates of glucose infusion. Hepatic glucose production measured by continuous infusion of 3-(3) H-glucose was similarly suppressed by both insulins to rates near zero. The metabolic clearance rate of glucose increased during infusion of human insulin by 120%, C-peptide levels decreased by 41% and plasma FFA concentrations fell by 74%. The respective changes during infusion of pork insulin were similar, 118%, 48% and 72%. Both insulins decreased the plasma levels of branched-chain amino acids, tyrosine, phenylalanine, methionine, serine and histidine similarly. Thus, the results demonstrate that semisynthetic human and porcine insulin are aequipotent with respect to suppression of hepatic glucose output, stimulation of glucose clearance, inhibition of insulin secretion, lipolysis and proteolysis.     

The asymmetry of the free amino acid pool in sections of the rat brain

The content of free amino acid pool in symmetric regions of cortex, hypothalamus, midbrain and blood of rats which had produced the movement conditioned reflex strengthened by feeding was studied. It was established that the "untrained" rats have higher content of free amino acid pool in their blood. The brain of the experimental animals revealed the biochemical asymmetry which was marked by the differences in free amino acid pool distribution between the left and right halves of the studied regions of brain. It was shown that left sided asymmetry animals i.e. animals with heightened content of free amino acid pool in the left half of the brain dominated in the "untrained" group of rats. The supposition was expressed that this biochemical asymmetry may contribute to the ability of animals to learn.     

Intracerebroventricular injection taurine changes free amino acid concentrations in the brain and plasma in chicks

Amino Acids - Brain amino acid metabolism has been reported to regulate body temperature, feeding behavior and stress response. Central injection of taurine induced hypothermic and anorexigenic...     

Purification and amino acid analysis of plasma acid stable trypsin inhibitor

Acid stable trypsin inhibitor (ASTI), with a molecular weight of about 85,000 by gel filtration, specific activity of 1,498 U/mg protein and pI of 1.6, from renal failure patient plasma was first purified. The amino acid composition of the purified ASTI was found to be that of a Gly- and Glu-rich protein which lacked His, closely resembling that of urinary trypsin inhibitor. The NH2-terminal amino acid sequence was Ala-Val-Leu-Pro-Gln-Glu- Glu-Glu-Gly-X-Gly-Gly-Gly-Gln-Leu-Val-Thr-Glu-Val-Thr-Lys-Lys-Glu- Asp-Ser-Ser-Gln-Leu-Gly-Tyr-Ser-Ala-Gly-Pro.     

Glutamate ingestion: the plasma and muscle free amino acid pools of resting humans

Monosodium glutamate (MSG) ingestion is known to increase plasma glutamate concentration, and MSG infusion stimulates insulin secretion. We investigated the impact of MSG ingestion on both the plasma and intramuscular amino acid pools. Nine postprandial adults ingested MSG (150 mg/kg) and rested for 105 min. Venous blood was sampled preingestion and then every 15 min; vastus lateralis muscle biopsies were taken preingestion and at 45, 75, and 105 min postingestion. Venous plasma glutamate and aspartate concentrations increased (P 相似文献   

Uptake of free plasma amino acids by the lactating cow''s udder and amino acid composition of udder lymph

1. Total α-amino N and the amounts of 24 ninhydrin-positive substances were determined in several samples of plasma and lymph from the cow's udder. The arteriovenous differences of these substances across the mammary glands were measured in several experiments performed on lactating cows and in one experiment on a `dry' cow. Udder lymph obtained from live lactating cows by a lymph fistula and taken after killing lactating cows was analysed. 2. The concentrations of the individual free amino acids in udder lymph obtained from the live cow were similar to those found in cow's plasma. The concentrations of many amino acids in udder lymph taken immediately after death were two- to four-fold higher than those of the corresponding amino acids in udder lymph obtained from the live cow. 3. Most amino acids of the blood showed a considerable decrease in concentration by passage across the lactating mammary gland. Ornithine, a non-casein amino acid, showed arteriovenous differences of up to 60% of the arterial plasma concentration. No substantial amino acid uptake by the udder could be demonstrated in the experiment on the non-lactating cow. 4. The arteriovenous differences obtained for arginine, glutamine, isoleucine, leucine, lysine, valine, threonine and histidine were probably large enough to provide all the respective amino acid residues in milk protein. 5. The uptake of aspartic acid, asparagine, glutamic acid, serine and proline by the lactating cow's udder was not sufficient to account for all these respective amino acid residues found in milk protein.     

Estimation value of plasma amino acid target analysis to the acute radiation injury early triage in the rat model

Rapid radiation injury early triage for large-scale people after radiation exposure is vital for limited medical resources allocation and early treatment of a large number of wounded after a nuclear accident. Owing to the high-throughput analysis and minimally invasive of collection sample, radiation metabolomics has been recently applied to radiation damage researches. Here, exploration the feasibility of estimating the acute radiation injury early triage by means of plasma amino acid target analysis was attempted using high performance liquid chromatography–electrospray tandem mass spectrometry (HPLC–ESI–MS/MS) technique. The nonlinear kernel partial least squares (KPLS) model was used to classify the radiation damage levels. The classification accuracy of without radiation exposure was 92.3 % at 5 h after exposure. At 24 h after exposure, the triage accuracies were all above 83 % in the different doses of irradiated groups, the correct classification rates of moderate and severe radiation injury were 91.7 and 92.3 % respectively. At 72 h after exposure, the classification accuracies of all levels of radiation injury were more than 90 %, the correct classification rates of moderate and severe groups were up to 100 %. This approach is useful for early predicting different levels of radiation exposure and for developing metabolomics strategies for radiation biodosimetry in humans, but need more data to consummate.     

Splanchnic free fatty acid kinetics

These studies were conducted to assess the relationship between visceral adipose tissue free fatty acid (FFA) release and splanchnic FFA release. Steady-state splanchnic bed palmitate ([9,10-(3)H]palmitate) kinetics were determined from 14 sampling intervals from eight dogs with chronic indwelling arterial, portal vein, and hepatic vein catheters. We tested a model designed to predict the proportion of FFAs delivered to the liver from visceral fat by use of hepatic vein data. The model predicted that 15 +/- 2% of hepatic palmitate delivery originated from visceral lipolysis, which was greater (P = 0.004) than the 11 +/- 2% actually observed. There was a good relationship (r(2) = 0.63) between the predicted and observed hepatic palmitate delivery values, but the model overestimated visceral FFA release more at lower than at higher palmitate concentrations. The discrepancy could be due to differential uptake of FFAs arriving from the arterial vs. the portal vein or to release of FFAs in the hepatic circulatory bed. Splanchnic FFA release measured using hepatic vein samples was strongly related to visceral adipose tissue FFA release into the portal vein. This finding suggests that splanchnic FFA release is a good indicator of visceral adipose tissue lipolysis.     

Effect of plasma free fatty acid concentration on the content and composition of the free fatty acid fraction in rat skeletal muscles.

Skeletal muscles contain a fraction of free (unesterified) fatty acids. This fraction is very small, but important since it contributes to the creation of the plasma-myocyte free fatty acid concentration gradient. Maintenance of this gradient is necessary for blood-borne fatty acids to be transported into the cell. There are no data on the regulation of the content and composition of the free fatty acid fraction in the cell. The aim of the present study was to examine the effect of an elevation and a reduction in the plasma-borne free fatty acid concentration on the content and composition of the free fatty acid fraction in different skeletal muscle types. The experiments were carried out on male Wistar rats with 280 - 310 g body weight. They were divided into four groups - 1, control; 2, exercised 3 h on a treadmill moving with a speed of 1,200 m/h and set at + 10 degrees incline; 3, treated with heparin; and 4, treated with nicotinic acid. Samples of the soleus as well as the red and white sections of the gastrocnemius muscles were taken. These muscles are composed mostly of slow-twitch oxidative, fast-twitch oxidative-glycolytic and fast-twitch glycolytic fibres, respectively. Lipids were extracted from the muscle samples and from the blood; the free fatty acid fraction was isolated by means of thin-layer chromatography. The individual free fatty acids were identified and quantified using gas-liquid chromatography. The plasma concentration of free fatty acids was as follows: control group, 236.1 +/- 32.9; after exercise, 407.4 +/- 117.5; after heparin, 400.8 +/- 36.8; and after nicotinic acid, 102.5 +/- 26.1 micromol/l (p < 0.01 vs. control values in each case). The total content of the free fatty acid fraction in the control group was as follows: white gastrocnemius, 27.6 +/- 7.3; red gastrocnemius, 52.2 +/- 13.9; soleus, 72.3 +/- 10.2 nmol/g. Elevation in plasma free acid concentration during exercise increased the total content of free fatty acids in the white gastrocnemius (38.7 +/- 13.9) and in the soleus (103.4 +/- 15.9 nmol/g; rest-exercise: p < 0.05 and p < 0.01, respectively), but had no effect in the red gastrocnemius. Neither elevation in the plasma free fatty acid concentration with heparin nor reduction with nicotinic acid affected the total content of the free fatty acid fraction in the muscles examined. The ratio of plasma concentration of individual acid to muscle concentration for the same acid varied greatly, depending on acid, muscle type and experimental group. The ratio was positive (above unity) for each acid almost in all cases with the exception of certain acids in the nicotinic acid-treated group where it was below unity. We conclude that the skeletal myocytes maintain a stable level of free fatty acid fraction in the wide range of plasma free fatty acid concentrations.