Biomedical subjects

R E Austic

Publications and source records attributed to R E Austic.

At least 19 recordsLinked to original sources

PubMed2001

Characterization of hepatic L-threonine dehydrogenase of chicken.

The L-threonine dehydrogenase (TDH) was purified approximately 1300-fold to a specific activity of approximately 18000 unit mg(-1) from chicken (Gallus domesticus) liver mitochondria. Purification was obtained by sequential chromatography on DEAE Cellulose, Phenyl Sepharose High Performance hydrophobic interaction, Affi-Gel Blue affinity and Matrex Gel Red A columns. The molecular weight of the subunit was estimated to be 36 kDa by sodium dodecyl-polyacrylamide gel electrophoresis. An apparent molecular mass of native protein between 62 and 74 kDa was obtained by gel filtration chromatography, suggesting a dimeric structure of TDH. The isoelectric point of TDH was determined by isoelectric focusing to be 5.3. Partial amino-terminal sequence analyses, carried out on two purified preparations of TDH, revealed a high degree of homology to the reported sequence of porcine TDH. The Michaelis constants for L-threonine and NAD for partially purified chicken hepatic TDH are 5.38 and 0.19 mM, respectively.

Alcohol Oxidoreductases↗

PubMed2001

Lysine and arginine requirements of broiler chickens at two- to three-week intervals to eight weeks of age.

Four experiments were conducted to determine the arginine and lysine requirements of male chickens for 2- to 3-wk intervals from the time of hatching until 8 wk of age. Weight gain, breast muscle growth, and feed efficiency were used as response for each interval. Dietary requirements for lysine and arginine were estimated by broken-line regression analysis of responses to six or seven dietary levels of each amino acid. Dietary crude protein levels were 22, 21, 20, and 18% in four consecutive experiments from 0 to 2, 2 to 4, 3 to 6, and 5 to 8 wk of age. An occasional estimate of requirement was not determined (ND) because the response did not conform to the regression model. The values for lysine and arginine requirements determined from breast muscle gain (weight gain of pectoralis major plus pectoralis minor) were not significantly higher than those from body weight gain. However, they tended to be higher than for feed efficiency for 0-to-2 and 2-to-4-wk-old broilers. Lysine and arginine requirements, as percentages of total amino acid in the diet, for maximum breast muscle growth were, respectively, 1.32+/-0.01% and 1.27+/-0.00% to 2 wk of age, 1.21+/-0.06% and ND for 2 to 4 wk of age, 0.99+/-0.02% and 0.97+/-0.02% for 3 to 6 wk of age, and 0.81+/-0.01% and 0.83+/-0.02% for 5 to 8 wk of age. Calculated digestible lysine and arginine requirements were, respectively, 1.24 and 1.19% to 2 wk of age, 1.11% and ND for 2 to 4 wk of age, 0.92% and 0.91% for 3 to 6 wk of age, and 0.75 and 0.78% for 5 to 8 wk of age. The requirements for lysine and arginine were similar except for the earliest age group for which the lysine requirement appeared to be slightly higher than that of arginine.

Age Factors↗

PubMed2001

The effect of dietary protein level on threonine dehydrogenase activity in chickens.

An experiment was carried out to determine the effect of dietary protein level on the specific activity of hepatic L-threonine dehydrogenase in young growing chicks. Six replicate pens of seven Leghorn chicks were fed semipurified diets containing 23, 27, or 32% CP with identical relative proportions of amino acids in each protein group. Body weights and feed consumption were measured for 3 d, and hepatic mitochondria were isolated for assay of threonine dehydrogenase (TDH) activity. Weight gains and feed efficiency increased at each level of protein supplementation, but feed consumption was not affected by protein level. The specific activity of threonine dehydrogenase in isolated liver mitochondria was significantly (P < 0.05) higher in the 32% CP group than in the 23% CP group, and the activity in the 27% CP group was intermediate. We conclude that moderate increases in dietary protein level result in elevated hepatic threonine dehydrogenase activity in growing chicks.

Alcohol Oxidoreductases↗

PubMed2000

Temporal response of hepatic threonine dehydrogenase in chickens to the initial consumption of a threonine-imbalanced diet.

Amino acid imbalances contribute to higher requirements of amino acids than would occur if the dietary profile of amino acids perfectly matched the requirements. The mechanisms of imbalances have not been fully elucidated. Because threonine dehydrogenase (TDH) activity in liver mitochondria increases in chicks and rats subjected to threonine imbalance, the current study was carried out to determine whether the change in TDH activity occurs rapidly enough after the consumption of an imbalanced diet to be considered a possible primary metabolic response. In a series of experiments, Leghorn chicks were allowed free access to a semipurified basal diet marginally limited in threonine or the same diet containing a mixture of indispensable amino acids (IAA) lacking threonine to cause a threonine imbalance. In the first experiment, dietary supplements of 5.5 and 11.1% IAA were used to determine a level of supplement that would cause a robust response in the specific activity of TDH. Feed intake, body weight gains and efficiency of feed utilization were lower and specific activities of TDH were higher in chicks fed 11.1% IAA than in those fed 5.5% IAA. In subsequent experiments, hepatic TDH activities and plasma amino acid profiles of the control and experimental groups were determined at 1. 5, 3, 6, 12 and 24 h after the first offering of the diet containing 11.1% IAA. The specific activities of TDH in chicks fed the IAA supplement were 40-150% higher (P < 0.05) and plasma threonine concentrations were 42-53% lower (P < 0.05) than in chicks fed the basal diet at all times except 1.5 h. These results indicate that changes in the capacity for threonine degradation via TDH may occur in the liver within a few hours after the consumption of a threonine-imbalanced diet and suggest the possibility that altered TDH activity may contribute to the increased threonine requirement associated with threonine imbalance.

Alcohol Oxidoreductases↗

PubMed2000

Isoleucine imbalance using selected mixtures of imbalancing amino acids in diets of the broiler chick.

Three experiments were conducted to determine the isoleucine requirement of a broiler from the time of hatch to 16 d of age. Chicks in the experiments were fed an isoleucine-limiting diet composed of wheat and peanut meal as the primary protein sources; this diet was used to investigate various mixtures of amino acids as imbalancing agents for isoleucine. The isoleucine requirement for maximum weight gain and feed efficiency was determined on the basis of broken-line regression analysis to be 0.63 to 0.65% of the diet or 3.28 to 3.38% of dietary protein. A similar diet, marginally limiting in isoleucine, was used to investigate the response of chicks to the addition of various mixtures of amino acids to the diet. Chicks that received a 5% dietary addition of 11 amino acids consisting of equimolar concentrations of leucine, valine, histidine, methionine, phenylalanine, tryptophan, tyrosine, alanine, glycine, serine, and threonine had significantly lower weight gain and feed consumption and a higher feed conversion ratio than did chicks fed the basal diet. These adverse effects were only partly prevented by an isoleucine supplement. The large neutral amino acids, histidine, methionine, phenylalanine, tryptophan, and tyrosine, accounted for most of the effect of the mixture. No effect of a mixture of leucine and valine or a mixture of the small neutral amino acids (alanine, glycine, serine, and threonine) at the same concentrations as those in the mixture of the 11 amino acids was observed. Lysine and arginine were the only two indispensable amino acids not present in the mixture of 11 amino acids. A subsequent experiment demonstrated that these amino acids did not become co-limiting with isoleucine when the diet was imbalanced with the amino acid mixture. These results indicate that an isoleucine imbalance in chicks is readily precipitated by excessive dietary concentrations of large neutral amino acids in diets that are otherwise marginally adequate in isoleucine.

Aging↗

PubMed1999

Effects of dietary mixtures of amino acids on fetal growth and maternal and fetal amino acid pools in experimental maternal phenylketonuria.

BACKGROUND: Branched-chain amino acids have been reported to improve fetal brain development in a rat model in which maternal phenylketonuria (PKU) is induced by the inclusion of an inhibitor of phenylalanine hydroxylase, DL-p-chlorophenylalanine, and L-phenylalanine in the diet. OBJECTIVE: We studied whether a dietary mixture of several large neutral amino acids (LNAAs) would improve fetal brain growth and normalize the fetal brain amino acid profile in a rat model of maternal PKU induced by DL-alpha-methylphenylalanine (AMPhe). DESIGN: Long-Evans rats were fed a basal diet or a similar diet containing 0.5% AMPhe + 3.0% L-phenylalanine (AMPhe + Phe diet) from day 11 until day 20 of gestation in experiments to test various mixtures of LNAAs. Maternal weight gains and food intakes to day 20, fetal body and brain weights at day 20, and fetal brain and fetal and maternal plasma amino acid concentrations at day 20 were measured. RESULTS: Concentrations of phenylalanine and tyrosine in fetal brain and in maternal and fetal plasma were higher and fetal brain weights were lower in rats fed the AMPhe + Phe diet than in rats fed the basal diet. However, fetal brain growth was higher and concentrations of phenylalanine and tyrosine in fetal brain and in maternal and fetal plasma were lower in rats fed the AMPhe + Phe diet plus LNAAs than in rats fed the diet containing AMPhe + Phe alone. CONCLUSION: LNAA supplementation of the diet improved fetal amino acid profiles and alleviated most, but not all, of the depression in fetal brain growth observed in this model of maternal PKU.

Amino Acids, Branched-Chain↗

PubMed1999

Influence of dietary arginine concentration on lymphoid organ growth in chickens.

In vivo effects of graded dietary levels of arginine on the body and lymphoid organs were investigated using Cornell K strain chickens of the B15/B15 haplotype. Two-week-old birds were fed an arginine-deficient basal diet (0.53% arginine) supplemented with additional arginine (up to 1.0% L-arginine to the diet). At four weeks of age, body weight, lymphoid organ weight, and concentrations of amino acids in plasma were measured. Arginine supplementation produced significant increases in plasma arginine (from 200 nM in chicks fed the basal diet to 2,000 nM in chicks receiving the 1.5% arginine diet) and ornithine concentrations (from 17 nM in chicks fed the basal diet to 500 nM in chicks receiving the 1.5% arginine diet). The arginine-deficient diet reduced body weight gain (P < 0.0001) and thymus, spleen, and bursa of Fabricius weights (P < 0.05). In contrast to the bursa weight, the thymus and spleen weights, as percentages of body weight, were also decreased (P < 0.05). This study suggests that arginine markedly influences lymphoid organ development, with a more pronounced effect on the thymus and spleen than on the bursa of Fabricius.

Amino Acids↗

PubMed1999

The recycling of L-citrulline to L-arginine in a chicken macrophage cell line.

L-Arginine is the only biological substrate of nitric oxide synthase in a reaction yielding NO and L-citrulline as co-products. The resynthesis of L-arginine from L-citrulline has been observed in murine macrophages. However, it is not known whether avian macrophages have a similar capacity for the synthesis of arginine. The present studies were carried out to determine whether L-citrulline can support NO (measured as nitrite) production in the HD11 cell, a chicken macrophage cell line. When added to media lacking L-arginine, L-citrulline supported a low level of nitrite accumulation: about 4 to 11% of the amount of nitrite formed from an equivalent concentration of L-arginine. Aspartic acid was not limiting for NO production from citrulline.

Animals↗

PubMed1999

Developmental pattern of phenylalanine hydroxylase activity in the chicken.

Experiments were conducted to determine the conditions for assay of hepatic phenylalanine hydroxylase (PAH) activity in the chicken and to determine the developmental pattern of PAH activity in liver 25,000 x g supernatant. PAH activity was detected in liver supernatant and (postnuclear) 25,000 x g particulate fraction. Optimum assay conditions differed for the two cell fractions, the most notable difference being a broad pH optimum of 7.7 to 9.2 for the supernatant and 4.7 and 5.6 for the particulate fraction. The PAH activity in the supernatant increased to a maximum as L-phenylalanine concentration in the assay medium increased from 0.02 to 0.5 mM and 1.0 mM. Activity increased in the particulate fraction as the Phe concentration increased to 0.5 mM. Substrate inhibition of PAH activity occurred at Phe concentrations of 3 to 5 mM in the supernatant but not in the particulate fraction. Concentrations of the cofactor, 6(R)-5,6,7,8-tetrahydrobiopterin, ranging from 0.09 to 0.75 mM, resulted in maximal PAH activity. The developmental pattern of PAH in supernatant was determined using a modified assay in which substrate and cofactor concentrations and pH were optimum. The PAH activity in liver supernatant was present at a low level in 11 d chick embryos and increased several fold between Days 15 and 17 to a maximum at Days 17 to 21. Activity declined at hatching to levels that were present in 11 to 15 d embryos and remained at this level in male chicks through 4 wk of age. Mature males had higher PAH activity than mature laying females.

Animals↗

PubMed1998

Transamination of 2-oxo-4-[methylthio]butanoic acid in chicken tissues.

The keto acid 2-oxo-4[methylthio]butanoic acid (OMTB) is an intermediate in the conversion of synthetic feed grade methionine sources to L-methionine in vivo in poultry and other animals. Because methionine sources are utilized by the chick with considerably less than 100% efficiency as sources of L-methionine, it is important to determine what metabolic process may limit the utilization of these sources. Because OMTB is converted to L-methionine by transamination, a study was conducted to determine which amino acids might serve as nitrogen donors in the conversion of OMTB to L-methionine in the chicken. Dialyzed tissue homogenates, mitochondria, and cytosol from liver, kidney, intestine, and skeletal muscle were incubated with OMTB and individual L-amino acids (isoleucine, leucine, valine, glutamic acid, aspartic acid, alanine, glutamine, asparagine, and phenylalanine) and the methionine that accumulated was determined by ion exchange chromatography. Tissues differed in the conversion of OMTB to methionine: kidney was most active, liver and intestinal mucosa were intermediate, and skeletal muscle had lowest activity. All amino acids supported methionine synthesis. Branched-chain amino acids and glutamic acid were the most effective substrates in tissue cytosols except in intestinal mucosa, in which asparagine was also effective. The preferred substrates in mitochondria were glutamate in liver mitochondria, isoleucine and alanine in kidney mitochondria, and branched-chain amino acids and glutamic acid in skeletal muscle mitochondria. All amino acids except alanine supported methionine synthesis from OMTB in mitochondria of intestinal mucosa. We conclude that a wide variety of amino acids can serve as substrates for transamination of OMTB in the chicken, and that the availability of nitrogen donors is unlikely to be a limiting factor in the conversion of OMTB to methionine.

Amino Acids↗

PubMed1998

The utilization of dipeptides containing L-arginine by chicken macrophages.

L-Arginine is the precursor of NO, a cytotoxic agent of macrophages. Studies were carried out to determine whether dipeptides containing arginine can be utilized by lipopolysaccharide (LPS)-activated avian macrophages for NO production. A chicken macrophage cell line, the HD11 cell, was used in all experiments. Peptidase activities were observed in fetal bovine serum (FBS) and macrophage serum free medium (Mac-SFM). Therefore, the utilization of dipeptides by macrophages was examined using Dulbecco's modified Eagle medium (D-MEM), a chemically defined medium, in short-term culture without FBS. Nitrite accumulation in the culture medium was used as the indicator of NO production. At concentrations of 0.15 mM in the culture media, L-leucinyl-L-arginine was 89% as effective as L-arginine in providing substrate for NO production. L-Argininyl-L-leucine was 38% as effective as L-arginine. The effectiveness increased to 93 and 58%, respectively, when the concentrations of dipeptides and arginine were 1.0 mM. Both values were slightly higher in a second experiment (97 and 70%, respectively). L-Lysine (10 mM) inhibited nitrite formation from all three sources of L-arginine. In studies of initial rates of transport by HD11 cells in Hanks Balanced Salts solution (HBSS), both L-argininyl-L-leucine and L-leucinyl-L-arginine inhibited arginine uptake. As lysine and arginine share a common transporter for cationic amino acids and are known to compete for transport, these studies suggest that the peptides were hydrolyzed extracellularly, yielding arginine that was transported into the cell where it served as a substrate for NO synthesis.

Animals↗

PubMed1997

Dietary protein and amino acid levels alter threonine dehydrogenase activity in hepatic mitochondria of Gallus domesticus.

Experiments were conducted to determine if hepatic threonine dehydrogenase (TDH) activity is influenced by dietary protein or specific amino acid concentrations. In an initial experiment, young chicks were deprived of feed for 60 h or had access for 72 h to a 22% protein basal diet, a protein-free diet or a 51% high protein diet. TDH activity was determined as aminoacetone and glycine accumulation during incubation of liver mitochondria. TDH activity was significantly (P < 0.01) lower in chicks fed the protein-free diet and significantly greater in chicks fed the high protein diet compared with chicks fed the basal diet. Food deprivation had no effect on TDH activity. A second experiment was conducted using the 22 and 51% protein diets, the 22% protein diet plus 1.14 g/100 g diet threonine (equivalent to the free plus protein-bound threonine content of the high protein diet), and the 51% protein diet containing 0.15 g/100 g diet less threonine. TDH was increased in chicks fed either high protein diet (P < 0.05). There were no significant differences in TDH activity, however, between chicks fed the basal diet and the threonine-supplemented diet or between chicks fed the two high protein diets. In two other experiments, the activity of TDH was investigated in chicks fed for 9 d dietary supplements of either serine or glycine (5.5 or 4 g/100 g basal diet, respectively). The supplements were added to the basal diet or the basal diet imbalanced by the addition of 6% branched-chain amino acids. Neither the serine nor the glycine supplement significantly altered TDH activity or the increased activity associated with a branched-chain amino acid-induced threonine imbalance. The results suggest that hepatic TDH activity is influenced by protein level or other amino acids more than by threonine itself.

Alcohol Oxidoreductases↗

PubMed1994

Dietary threonine imbalance alters threonine dehydrogenase activity in isolated hepatic mitochondria of chicks and rats.

Experiments were conducted on chicks and rats to determine whether hepatic threonine dehydrogenase activity is modified by the consumption of a threonine-imbalanced diet and to determine the tissue distribution of this enzyme. Threonine imbalances were created by supplementing basal diets with branched-chain amino acids (6 g/100 g diet for chicks) or a mixture of indispensable amino acid (5.6 g/100 g diet for chicks and 5.4 g/100 g diet for rats). Chicks fed threonine-imbalanced diets consistently had twice the hepatic threonine dehydrogenase activity of those fed the basal diet when measured in one experiment at 24 h and in two experiments at 216 h (P < 0.05). Rats received the experimental diets for 12 or 24 h in one experiment and for 12, 24, 72 or 168 h in another experiment. In the first experiment, rats fed the threonine-imbalanced diet had significantly greater hepatic threonine dehydrogenase activity (P < 0.05) at 12 h but not at 24 h. In the other rat experiment, threonine dehydrogenase activity in the rats fed the threonine-imbalanced diet was significantly greater than in controls at 72 h, but tended to be lower at 168 h, which coincided with the adaptation of the rats to the imbalanced diet. Threonine dehydrogenase activity was widespread in tissues of both species. The results indicate that alterations in hepatic threonine dehydrogenase activity occur in chicks and rats subjected to threonine imbalance.

Acetone↗

PubMed1994

Threonine requirement and threonine imbalance in broiler chickens.

Three experiments were conducted to determine the effect of excess dietary protein on threonine requirement of broiler chicks to 14 d of age (Experiments 1 and 2) and to determine the threonine requirement from 16 to 28 d of age (Experiment 3). Two dietary protein levels were used in Experiments 1 and 2:20% CP in a threonine-limiting basal diet containing wheat, peanut meal, and selected amino acids and 25% CP in the same basal diet supplemented with a mixture of amino acids lacking threonine. A threonine-limiting 25% CP diet based on corn, soybean meal, and amino acids was also included in Experiment 2. The threonine requirement of chicks from 16 to 28 d of age was determined using a single CP level (20%) in Experiment 3. Threonine requirements were estimated by broken line regression analysis of weight gain and feed efficiency. Threonine requirements based on weight gain were 7.7 and 6.7 g/kg of diet in Experiments 1 and 2, respectively, for chicks receiving the 20% CP diets. The requirements increased to 8.6 and 8.2 g/kg, respectively, for chicks fed the 25% CP diets based on wheat, peanut meal, and amino acids. The requirement for maximum weight gain of chicks fed 25% CP based on corn, soybean meal, and amino acids was 7.7 g/kg of diet. However, chicks ate more of this diet, and on an intake basis, the requirement of the chicks fed the 25% CP diets based on wheat and peanut meal or corn and soybean meal did not differ. Requirements based on feed efficiency were equal to, or less than, those based on weight gain in Experiments 1 and 2. Body moisture and fat contents were affected by dietary CP level (P < .01), ingredient composition (P < .01), and threonine content (P < .05). Estimates of threonine requirements based on regression analysis of plasma threonine concentrations were higher than those based on weight gain or feed efficiency. The threonine requirements of chicks fed a 20% CP diet from 16 to 28 d of age were 6.3 and 6.9 g/kg of diet based on weight gain and feed efficiency, respectively.

Animal Feed↗

PubMed1994

Environment-immune interactions.

The need for effective immune function for the maintenance of health has been clearly established in both agriculturally significant animal species and humans. Intensive agricultural practices present production species with numerous disease challenges during the rearing period. Environmental factors represent a ubiquitous, yet frequently manageable, category of immunomodulators that can influence immune performance and ultimately disease susceptibility or resistance. However, strategies for assessing overall immune potential have not been widely implemented for agricultural species. This is in contrast to the use of immune evaluation for human health considerations. Immune assessment relative to environmental-immune interactions can produce benefits in two areas. First, the efficiency of the production operation can be enhanced. Second, the welfare of the animals during the production cycle can be optimized. This paper presents an overview of environmental factors known to influence the immune function of poultry and the opportunities to manage environmental factors to benefit the health of the animals. In addition, the paper discusses the status of immunological assessment for humans and laboratory animals and proposes potential immune assessment panels that could serve as a tool to optimize the environmental management of poultry populations.

Animal Husbandry↗

PubMed1993

Effects of selected minerals on acid-base balance and tibial dyschondroplasia in broiler chickens.

Experiments were conducted to determine the relative acidogenicities of several anions, including chloride, sulfate, and mono-, di-, and tribasic phosphate in commercial broiler chickens. Graded levels (80 and 160 meq/kg of diet in two experiments; 50, 100, and 150 meq/kg in a third experiment) of all anions were substituted as calcium salts on a molar equivalent basis for calcium carbonate in a semipurified diet. All diets contained equivalent amounts of calcium. The occurrence of tibial dyschondroplasia was determined by visual scoring of the epiphyseal growth plate in the distal end of the tibiotarsus. None of the anions added to the diet at levels of 160 meq/kg or less affected body weight or feed consumption. A higher level of chloride (240 meq/kg) that was utilized in some experiments decreased weight gain by 16 to 22%. All anions except tribasic phosphate resulted in reduced blood pH or bicarbonate concentrations or both. Monobasic phosphate was more acidogenic than dibasic phosphate and sulfate and chloride was the most acidogenic of all mineral anions. All anions including tribasic phosphate increased the severity of tibial dyschondroplasia. There was no consistent relationship between blood pH, bicarbonate concentration, or partial pressure of CO2 and the severity of tibial dyschondroplasia.

Acid-Base Equilibrium↗

PubMed1992

Direct measurement of nitric oxide in headspace gas produced by a chicken macrophage cell line in a closed culture system.

A simple and rapid method was applied for direct measurement of nitric oxide (NO) gas produced by cultured macrophages using a modified chemiluminescence detector, the thermal energy analyzer (TEA). HD11 chicken macrophages (1-3 x 10(6)/ml) were cultured on microcarrier beads (100 mg/ml) in 140 ml air-tight glass jars (5 ml cell suspension per jar) containing 0.5 micrograms/ml of LPS and different concentrations of L-arginine. Headspace gas was sampled at 24 hours of culture via a rubber septum and directly injected into a TEA with a liquid nitrogen trap set at -130 to -140 degrees C. The concentration of NO in the gas sample was quantified using a standard gas mixture of NO (2 microliters/L) in nitrogen. Gas samples from L-arginine-supplemented cultures contained NO (0.028-0.066 pl/microliter), whereas NO was not detected in samples from controls. These results suggest that chicken macrophages synthesize NO gas in a dose-dependent manner relative to L-arginine concentration.

Animals↗

PubMed1992

Dietary arginine influences Rous sarcoma growth in a major histocompatibility B complex progressor genotype.

L-Arginine (L-Arg) can serve as a substrate for the production of reactive nitrogen intermediates. One of these metabolites, nitric oxide, has been shown to possess significant antitumor properties in vitro. To investigate the importance of this system in vivo, we have examined the dietary L-Arg host tumor interaction in the chicken. Since chickens are incapable of de novo L-Arg synthesis, concentration of this amino acid is readily controlled by diet. Line UNH 105 New Hampshire chickens having the major histocompatibility complex genotype, B24/B24, were used to study in vivo effects of dietary L-Arg on Rous sarcoma growth. After 5 weeks on a standard diet, 119 chicks were fed either a basal (0.92% L-Arg) diet or a high arginine (2.40% L-Arg) diet. One week later, chicks were wing-web inoculated with subgroup A Rous sarcoma virus. Tumor growth was monitored weekly for 12 weeks after inoculation. Plasma L-Arg levels and body weights from birds on each dietary treatment were analyzed. Neither body weight gains nor latent period for tumor development was affected by diet. However, plasma L-Arg levels were significantly different between dietary treatments (basal, 0.245 +/- 0.01 mumol/ml; high, 0.738 +/- 0.03 mumol/ml). In addition, mean tumor size scores were significantly (P less than 0.05) lower over time in chickens fed the high L-Arg diet. The results suggest that dietary L-Arg in excess of the amount required for growth reduces tumor load.

Animals↗