共查询到20条相似文献，搜索用时 31 毫秒
1.
Incubations of bovine ileal mucosa were used to identify the amino acid transport systems responsible for methionine and lysine uptake in cattle small intestine. Uptake was expressed as micromole per milliliter of cell water. Lysine uptake was shown to be sodium (Na) independent. Specific transport components of lysine uptake were estimated to be: 63% occurring through the cationic (Y+) system, 17% via the neutral alanine (A) and alanine, serine, cysteine (ASC) amino acid transport systems, and 20% through nonsaturable processes. Physiological concentrations of competitive inhibitors altered (P less than .05) lysine uptake. Methionine uptake was shown to occur by both Na-independent and Na-dependent transport systems. The specific transport components of methionine uptake were estimated as 54% occurring through the neutral branched chain leucine (L) systems, 28% through the ASC system, 15% through the A system and 25% through nonsaturable processes. Physiological concentrations of competitive inhibitors did not inhibit (P greater than .05) methionine uptake. 相似文献
2.
Lysine and methionine transport by bovine jejunal and ileal brush border membrane vesicles 总被引：2，自引：0，他引：2
Lysine (LYS) and methionine (MET) transport were studied using brush border membrane vesicles from bovine jejunal and ileal tissues. Total transport of LYS and MET was divided into mediated and diffusion components. Mediated uptake was further divided into sodium (Na)-dependent and Na-independent systems. Total LYS and MET uptake by ileal brush border (BB) vesicles tended to be higher than that by jejunal BB vesicles at all concentrations evaluated but differences were significant (P less than .05) at 2.5 and 7.5 mM for LYS and 5, 12.5 and 15 mM for MET. The greater capacity of ileal BB vesicles appeared to be due to the Na-dependent component of LYS uptake and the diffusion component of MET uptake. Transporters had less affinity but higher capacity than for LYS transport in both ileal and jejunal tissue. Methionine transport was greater (P less than .05) than LYS transport in both ileal and jejunal BB vesicles when the initial amino acid concentration was 7.5 mM. But when the initial amino acid concentration was 1.25 mM, MET uptake was greater (P less than .13) than LYS uptake in jejunal, but not in ileal, BB vesicles. The relative contribution of mediated and diffusion uptake systems to total MET and LYS uptake was found to be dependent on substrate concentration. Both intestinal site and substrate concentration influenced the contributions of Na-dependent, Na-independent and diffusion systems to total methionine and lysine uptake. 相似文献
3.
Kinetic properties and substrate specificity of the lysine transport system in porcine mammary gland were studied using mammary tissue explants from nine lactating sows. Sodium dependence of lysine uptake was determined by replacing sodium in the medium with choline. Kinetic parameters of lysine uptake were determined using lysine concentrations from 5 microM to 5.12 mM. Competition of lysine uptake by other amino acids was determined using the cationic amino acids, arginine and ornithine, and using other essential amino acids. Transport of lysine was time-dependent and was unaffected by replacing sodium with choline. Lysine uptake occurred by a transport mechanism with a Km of approximately 1.4 mM and a Vmax of 7.9 mmol x kg cell water(-1) x 30 min(-1). Lysine uptake was inhibited by arginine and ornithine and by high concentrations of L-alanine, L-methionine, L-leucine, cycloleucine, and D-lysine, but not by 2-(methylamino)-isobutyric acid. This transport mechanism is the primary system responsible for uptake of cationic amino acids in lactating sow mammary tissue. The relatively high Km, compared with physiological blood concentrations of lysine, indicates that the kinetic properties of the lysine transport system should not be limiting to milk protein synthesis. Transmembrane transport of lysine by lactating sow mammary tissue should be a direct function of plasma concentrations. However, interactions of other amino acids with the uptake system may affect lysine uptake. 相似文献
4.
1. A study was conducted to characterise the development of amino acid transport in broiler chicks, using L-tryptophan as a model. The chicks were maintained on a broiler starter diet between hatch and 21 d of age. 2. There was a significant reduction in the rate of uptake of 0.04 mM L-tryptophan with age in both the jejunum and ileum. Uptake was enhanced in the presence of 50 mM sodium chloride to different degrees depending on age and intestinal site. At both intestinal sites, uptake capacity increased with age while there was a reduction in uptake efficiency with age. 3. At a concentration of 25 mM, both sodium chloride and potasium chloride increased uptake by ileal brush-border membrane vesicles (BBMV) of 7-d-old chicks but uptake was reduced when potassium chloride was included at a concentration of 50 mM. In the presence of valinomycin, uptake by jejunal BBMV was stimulated by 25 mM sodium chloride. In the presence of both sodium chloride and potassium chloride and in the absence of valinomycin, uptake was increased by 42.6% but this was reduced to 23.4% when the ionophore was included in the buffer. 4. The Na+-independent uptake of L-tryptophan into jejunal vesicles of 21-d-old chicks was lower in the presence of D-tryptophan than in the presence of 2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid (BCH). The inclusion of BCH in the incubation medium at low concentrations significantly enhanced the uptake of 0.04 mM L-tryptophan by jejunal BBMV. 5. At similar concentration (0.04 mM) to L-tryptophan, lysine, methionine and alanine in the presence of Na+ also stimulated L-tryptophan uptake. The uptake of L-tryptophan was reduced at a higher concentration, 25 mM, of these amino acids. 6. The study revealed a decline in rate of amino acid uptake and an increase in total uptake capacity with age. Tryptophan uptake was both Na+-independent and dependent, and occurred more in the ileum than in the jejunum. The uptake of L-tryptophan depended on the concentration of other amino acids and other factors in the diet and digesta. 相似文献
5.
J. A. Nolles I. G. S. Peeters B. I. Bremer R. Moorman R. E. Koopmanschap M. W. A. Verstegen V. V. A. M. Schreurs 《Journal of animal physiology and animal nutrition》2008,92(5):529-537
In the present study, the effect of free amino acid (FAA) diets on the intestinal absorption rate of methionine and leucine was studied ‘ex vivo’ with rats adapted for different periods of time to the diets, using the everted sac method. The adaptation period to the 21% FAA diet with an amino acid content based on casein was either, 0 (no adaptation, N‐ADA), 5 (short‐term adaptation, ST‐ADA), or 26–33 days (long‐term adaptation, LT‐ADA). Within the ST‐ADA and the LT‐ADA groups, three different levels of methionine were included: 50%, 100% and 200% of the level normally present in casein. All diets were iso‐nitrogenous and iso‐caloric. After the adaptation period (0, 5, or 26–33 days), intestinal everted sacs were prepared. Methionine or leucine was added to the medium as transport substrate. The methionine absorption rate of the rats of the LT‐ADA groups was higher than that of the N‐ADA groups. Furthermore, adaptation to 200% dietary methionine levels caused a significantly slower leucine absorption compared to the 100%, and 50% group. Methionine absorption was similar in the 100% and 200% groups, but the absorption of methionine in the 50% group was enhanced in the distal part of the intestines. We concluded that in response diets with 21% FAAs as only amino acid source, amino acid absorption is decreased to avoid toxic effects of high levels of methionine in the circulation. 相似文献
6.
The effects of adding lysine and/or methionine to a ration of calculated deficiency in these amino acids of 10% and 20%, respectively, were studied in 24 Brown Swiss cows. The mixed rations (27% grass silage, 19% maize silage, 5% hay and 49% concentrate on DM basis) contained 14.5% CP on average. Lysine supply was selectively elevated by adding fish meal in exchange for other concentrate ingredients. Methionine was supplied in a rumen-protected form. Milk protein content was elevated whereas fat amount decreased by adding both amino acids. Lactose content increased without additional lysine from fish meal. Live weight, milk yield, milk fat content and protein amount remained unaffected by any variation of amino acids supply. Also nutrient digestibility and nitrogen balance were not changed by the treatments. Blood plasma concentrations confirmed the assumed variation in metabolic lysine and, less clear, methionine supply. Effects on plasma concentrations of other amino acids were relatively small. Most plasma hormones and enzymes, and metabolites in plasma, urine and milk did not respond to the variation in amino acid supply. Lysine addition via fish meal increased aspartate amino transferase and decreased urinary allantoin concentration. Additional methionine elevated plasma ornithine. Overall lysine and methionine appear to have been only marginally deficient in the unsupplemented ration fed for 3 weeks despite the deficiency of 10% to 20% as calculated by the I.N.R.A. method. 相似文献
7.
Lixiang Chen Yu-Long Yin Wenjuan S. Jobgen Scott C. Jobgen Darrell A. Knabe Wei-Xin Hu Guoyao Wu 《Livestock Science》2007,109(1-3):19-23
This study was conducted to test the hypothesis that porcine jejunal mucosal cells can degrade all essential amino acids (EAA). Jejunal mucosal cells (primarily enterocytes) were isolated from 50-day-old healthy pigs and incubated at 37 °C for 45 min in Krebs buffer containing plasma concentrations of amino acids and one of the following l-[1-14C]- or l-[U-14C]-amino acids plus unlabeled tracers at 0.5, 2, or 5 mM: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. There was active transamination of leucine, isoleucine and valine in the cells (1.35–2.5 nmol/mg protein per 45 min at 2 mM), with most (67–71%) of their -ketoacids released into the medium. In contrast, catabolism of methionine and phenylalanine was negligible (0.04–0.05 nmol/mg protein per 45 min at 2 mM) and that of other EAA was completely absent in these cells. These results indicate that intestinal mucosal cells are a site for the substantial degradation of branched-chain amino acids but not other EAA in pigs. 相似文献
8.
Cyst membranes of Cysticercus tenuicollis, the larval stage of Taenia hydatigena, contained 14 amino acids, namely lysine, histidine, arginne, aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, isoleucine and leucine. Methionine was present in traces. In comparison, the cyst fluid was deficient in histidine, arginne, threonine, methionine and valine and the scolices did not have threonine, serine, glutamic acid and methionine. The membrane contained large quantities of amino acids in comparison to the other components of the cyst. 相似文献
9.
Zuzana Ceresnáková A Sommer Mária Chrenková Patrícia Dolesová 《Archives of Animal Nutrition》2002,56(6):409-418
The crude protein content and amino acid profile of seven feedstuffs (linseed meal, maize gluten meal, rapeseed meal, rapeseed meal protected, soybean meal, fullfat soybean extruded and sunflower meal) were determined before and after ruminal incubation for 16 h in three bulls with large rumen cannulas. The intestinal disappearance of amino acids was measured using mobile bag technique. Ruminal incubation affected amino acid profile of all experimental feedstuffs. Crude protein degradation varied from 29.3% for maize gluten meal to 86.4% for rapeseed meal. A tendency towards increased disappearance was observed for glutamic acid, histidine, lysine and proline and decreased disappearance for branched-chain amino acids. The intestinal crude protein digestibility was higher than > 80%, except rapeseed meal (66.4%) and sunflower meal (77.8%). The least digestible individual amino acids were methionine and isoleucine in rapeseed meal, histidine and methionine in rapeseed meal protected and arginine in sunflower meal. In general, the lowest amino acid digestibilities were found in feedstuffs with the highest fibre content. The feedstuffs show that they have different potential for supplying of limiting amino acids. Of particular value are the feedstuffs with low crude protein degradability in the rumen and high intestinal digestibility of amino acids. 相似文献
10.
研究反刍动物氨基酸需要量的最常用方法为屠体氨基酸分析法和真胃或十二指肠灌注法 ,研究者们采用不同的方法研究了肉牛的氨基酸需要量。在生长肉牛的实用日粮条件下 ,蛋氨酸或赖氨酸常为第 1限制性氨基酸 相似文献
11.
Mucosa obtained from the cecum of healthy horses and incubated in vitro with 0.1 mM cycloleucine could accumulate this amino acid against an apparent concentration gradient after 60 and 120 minutes. Accumulation by the serosal (antiluminal) surface of the tissue was 3 times greater than accumulation by the mucosal (luminal) surface after 120 minutes (P less than 0.001). Cycloleucine accumulation was significantly reduced by Na deprivation after 60 minutes (P less than 0.05) and 120 minutes (P less than 0.01) and by anoxic conditions after 120 minutes (P less than 0.05). Transmucosal flux from mucosal to serosal surface of the tissue was significantly (P less than 0.05) greater than the opposing flux, but both unidirectional fluxes were small and were largely attributed to passive processes. It was concluded that the most avid transport system for cycloleucine was on the serosal surface of the horse's cecal mucosa, and an active transport system was not evident on the mucosal surface. An active transport system for amino acids on the serosal surface could be explained by the need for crypt cells, the predominant epithelial cell type in the cecum, to obtain nutrients from blood, rather than from the intestinal lumen. 相似文献
12.
D E Freeman A Kleinzeller W J Donawick V A Topkis 《American journal of veterinary research》1989,50(12):2138-2144
When sheets of mucosa from the cecum of clinically normal horses were incubated in vitro with radiolabeled L-alanine, they could accumulate this amino acid against an apparent concentration gradient after 60 to 150 minutes of incubation. The active transport system for L-alanine was on the serosal surface of the mucosal sheet only. L-Alanine accumulation at 60 minutes was partly inhibited by 20 mM glycine (P less than 0.01), 0.5 mM ouabain (P less than 0.05), and Na deprivation (P less than 0.02). Anoxia for 60 minutes increased L-alanine accumulation, but had adverse effects on cell structure and intracellular cation distributions. Transmucosal fluxes induced a small, but significant (P less than 0.05), net secretion of L-alanine, and the mean (+/- SEM) transmucosal potential difference was 7.3 +/- 0.7 mV over the period of flux measurement. It was concluded that L-alanine was accumulated by the serosal surface of the cecal mucosa, possibly to provide substrate for tissue metabolism. There was no evidence that the cecal mucosa could actively transport this amino acid from the luminal bathing medium. 相似文献
13.
Tuula Dahlman Jarmo Valaja Paavo Niemelä Taina Jalava 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(4):174-182
The influence of dietary protein content and composition on growing-furring blue fox ( Alopex lagopus ) was studied with three protein levels [15%, 22.5% and 30% of metabolizable energy (ME) from protein]. The two lowest diets were fed as such, or as supplemented with L-methionine or lysine. Growth, from the start of the experiment in July to mid-September, improved with increasing protein level ( P < 0.01). Lysine supplementation, unlike methionine, decreased early growth ( P <0.05). During the last months of the experimental period, differences in weight gain between the groups evened out. Skin length and quality declined with decreasing protein level ( P <0.05). Methionine and lysine had opposite effects on skin length ( P <0.10). For normal body growth and skin length, a level of 0.40 g of digestible L-methionine MJ -1 ME, and 25-32% protein in feed dry matter, was required. When feed ingredients are deficient in methionine, a supplementation is recommended. Methionine is the first limiting amino acid of the two amino acids studied here. 相似文献
14.
乳蛋白是体现牛奶质量的重要指标,乳蛋白氨基酸来源于日粮氨基酸。乳蛋白中酪蛋白、乳白蛋白和乳球蛋白除了满足人体基本营养需求,还对人体生长、发育和健康发挥重要作用,是动物源优质蛋白质来源。蛋氨酸与赖氨酸是奶牛日粮限制性氨基酸,不仅是乳蛋白合成的重要底物,同时还作为信号分子调控乳蛋白基因表达。本文综述了奶牛氨基酸需要与来源、必需氨基酸、限制性氨基酸、保护性蛋氨酸和赖氨酸在日粮中的应用,阐述了氨基酸营养在蛋白质合成代谢中的核心作用,为指导奶牛日粮配方提供参考。 相似文献
15.
The cellular uptake of branched-chain amino acids in mammary tissue is important for understanding their role in milk synthesis in the sow. This study characterized the kinetic properties and substrate specificity of the valine uptake system in the porcine mammary gland. Mammary tissue was collected from lactating sows at slaughter and tissue explants were incubated in media containing isosmotic salt and amino acids of interest, plus [3H]valine tracer. Valine uptake was time-dependent and was dependent on the presence of sodium, as indicated by a reduction in uptake when sodium in the medium was replaced by choline. The valine transport system in porcine mammary tissue had a Km of 0.64 mM, a Vmax of 1.84 mmol-kg cell water(-1) 30 min(-l), and a Kd (diffusion constant) of 1.16 L x kg cell water(-1) x 30 min(-1). Valine uptake was inhibited by leucine and alpha-aminoisobutyric acid and by high concentrations of L-alanine, L-lysine, cycloleucine, L-glutamine, and L-methionine, but not by 2-(methyl-amino)-isobutyric acid. This transport system is the primary system responsible for uptake of valine, and probably other branched-chain amino acids, in lactating sow mammary tissue. Physiological concentrations of valine in the blood are below the Km of the specific valine transport system and well below the diffusion uptake capabilities. The kinetic parameters of this valine transport system should not be limiting to valine uptake for milk protein synthesis. However, competition of valine uptake with branched-chain amino acids, as well as with other amino acids, may affect valine uptake in lactating tissue. 相似文献
16.
以泌乳中后期奶牛为试验对象，研究了瘤胃补充保护蛋氨酸及十二指肠灌注蛋氨酸对生产性能、乳成分及氮代谢的影响，结果表明：瘤胃补充保护蛋氨酸及十二指肠灌注蛋氨酸能显著增加血浆尿素氮、血浆甘油三酯、奶中尿素氮浓度（P〈0．05），对产奶量、乳成分、瘤胃液氨氮、血浆葡萄糖无显著影响（P〉0．05）。 相似文献
17.
1. Three trials were carried out in order to determine the amount by which dietary protein concentration can be reduced while maintaining the dietary concentrations of the first two limiting amino acids, methionine and lysine. 2. In all trials growth rate and food utilisation declined as the protein concentration of a well-balanced standard chick diet was lowered by replacing soybean meal with sorghum grain (milo), but this trend could be partly or completely prevented when methionine or methionine and lysine levels were restored. 3. Addition of 0-06 to 0-07% methionine, above that considered to be normal, is sufficient to replace approximately 0.9% soybean protein. 4. In diets containing approximately 3 percentage units less soybean protein than required, a supplementation of about 0.15% each of methionine and lysine can replace nearly 2-0% soybean protein, but cannot bring about chick performance equal to that obtained on the control ration, indicating an insufficiency of a third, or third and fourth, limiting amino acid in such low-protein diets. 相似文献
18.
19.
Utilization of grass silage by growing cattle: effect of a supplement containing ruminally protected amino acids. 总被引：2，自引：0，他引：2
Sixteen crossbred steers (278 +/- 4.9 kg) were used to determine the influence of supplemental ruminally protected lysine and methionine on performance of growing cattle fed grass silage. During the 154-d experiment, all steers were allowed ad libitum consumption of a good-quality grass silage during the first 70 d and of a lesser-quality silage during the remaining 84 d of the trial. The steers received a supplement of .5 kg/d of barley with or without a mixture of ruminally protected amino acid (RPAA) containing 8.2 g of lysine and 2.6 g of methionine. Compared with controls, steers supplemented with RPAA showed 16.3% improved (P less than .03) ADG (.92 vs 1.07 kg/d). Dry matter intake was not affected (P greater than .50) by treatment and averaged 2.03% BW across treatments. Supplementation with RPAA improved feed/gain by 13.6% (7.88 vs 6.81 for control and RPAA treatments, respectively, P less than .01). Plasma levels of methionine, lysine, arginine, and glutamic acid were higher (P less than .05) and of histidine were lower (P less than .001) when RPAA were fed. These results indicate that feeding RPAA can improve the performance of growing steers fed grass silages of varying qualities. 相似文献
20.
Adverse effects of excess methionine were examined using 12 Holstein bull calves trained to maintain reflex closure of the reticular groove even after weaning at 5 wk of age. Two nitrogen balance experiments were conducted for 2 wk each from 6 wk (Stage 1; BW = 62 kg) and 12 wk of age (Stage 2; BW = 103 kg) by dividing the calves into three groups at each stage. Calves were fed a corn-soybean meal diet at 62 g/kg of metabolic BW at both stages. At Stage 1, feed efficiency (gain:feed intake) and nitrogen retention did not differ between the group supplemented with .333 g of DL-methionine and .111 g of L-lysine monohydrochloride/kg BW per day and the group supplemented with isonitrogenous diammonium citrate, although the level of DL-methionine was considered to be enough to induce toxicity. Conversely, administration of isonitrogenous casein increased nitrogen retention. At Stage 2, administration of the same levels of methionine and lysine resulted in reduced feed intake, depressed nitrogen retention, and BW loss. Conversely, administration of the isonitrogenous casein did not increase nitrogen retention compared with the supplement of isonitrogenous diammonium citrate. Administration of excess methionine and lysine increased plasma methionine concentrations up to 230 (Stage 1) or 190 micromol/dL (Stage 2). Plasma lysine concentrations were less than 24 micromol/dL at every stage. Administration of the amino acid mixture decreased plasma concentrations of branched-chain amino acids and phenylalanine more obviously at Stage 2 than at Stage 1. These results indicated that abomasal administration of .333 g of DL-methionine/kg BW per day induced methionine toxicity at Stage 2 but methionine imbalance at Stage 1. 相似文献