Increase In Alanine Concentration Research Articles

Effects of crude protein intake from forage‐only diets on muscle amino acids and glycogen levels in horses in training

There is little information about the influence of crude protein (CP) intake on glycogen and free pool amino acid concentrations in the muscle of horses in training. High energy forage-only diets may be an alternative to concentrate rich diets and may provide high levels of CP. To study the effect of feeding 2 forage-only diets, containing either high or moderate CP concentrations on glycogen and free pool amino acid concentrations in the muscle. Two high energy forage-only diets based on high-energy grass forage were fed for 23 days in a crossover design to 6 Standardbred horses in racing condition. One forage diet provided a high (HP) CP (16.6%) intake and the other diet provided recommended intake (RP) of CP (12.5%). At Day 19 a standardised treadmill test was performed to mimic a race. Blood samples were taken before, during and after (up to 90 min) the treadmill test and muscle biopsies (m. gluteus) were taken before and after exercise and after 90 min. Amino acids were analysed with a HPLC-technique and glycogen with a fluorimetric method. A main effect of the HP diet was that muscle glycogen and leucine concentrations were higher compared to the RP diet. Branched chain amino acid concentrations in plasma remained higher during early recovery from exercise on the HP diet compared to the RP diet. Intense exercise caused a similar decrease in glycogen, aspartate and glutamate concentrations in muscle and increase in alanine concentration on both diets. Feeding a forage-only diet with a high CP intake increases glycogen and leucine concentrations in muscle of horses in training. This may be beneficial for muscle recovery following intensive exercise.

Variation in the content of free amino acids in body fluids of freshwater mollusk Lymnaea stagnalis during seasonal adaptation to low positive temperatures

The effect of autumn and winter decrease in environmental temperature on the content of free amino acids in body fluids has been studied in freshwater snail Lymnaea stagnalis. In autumn, when temperature drops to 4 and 0°C, the highest increase in alanine concentration was observed and its pool was almost three times that in summer. A less pronounced accumulation of glutamate, glycine, histidine, and serine was observed in the same temperature range. Cysteine was detected at 0°C. The accumulation of essential amino acids methionine, leucine, isoleucine, tyrosine, and phenylalanine took place at 0°C, while only traces of these amino acids were detectable at 4°C. At the same time, free lysine undetectable in summer has been revealed in autumn at 4°C and its concentration increased as temperature decreased to 0°C. In winter, when the mollusks were hypermetabolic for 2.5 months, the pools of all amino acids decreased 4–8 times, while essential amino acids (except lysine) were undetectable. The involvement of alanine and, possibly, lysine in L. stagnalis adaptation to near-zero temperature is proposed.

Effect of endurance training on muscle TCA cycle metabolism during exercise in humans.

We tested the theory that links the capacity to perform prolonged exercise with the size of the muscle tricarboxylic acid (TCA) cycle intermediate (TCAI) pool. We hypothesized that endurance training would attenuate the exercise-induced increase in TCAI concentration ([TCAI]); however, the lower [TCAI] would not compromise cycle endurance capacity. Eight men (22 +/- 1 yr) cycled at approximately 80% of initial peak oxygen uptake before and after 7 wk of training (1 h/day, 5 days/wk). Biopsies (vastus lateralis) were obtained during both trials at rest, after 5 min, and at the point of exhaustion during the pretraining trial (42 +/- 6 min). A biopsy was also obtained at the end of exercise during the posttraining trial (91 +/- 6 min). In addition to improved performance, training increased (P < 0.05) peak oxygen uptake and citrate synthase maximal activity. The sum of four measured TCAI was similar between trials at rest but lower after 5 min of exercise posttraining [2.7 +/- 0.2 vs. 4.3 +/- 0.2 mmol/kg dry wt (P < 0.05)]. There was a clear dissociation between [TCAI] and endurance capacity because the [TCAI] at the point of exhaustion during the pretraining trial was not different between trials (posttraining: 2.9 +/- 0.2 vs. pretraining: 3.5 +/- 0.2 mmol/kg dry wt), and yet cycle endurance time more than doubled in the posttraining trial. Training also attenuated the exercise-induced decrease in glutamate concentration (posttraining: 4.5 +/- 0.7 vs. pretraining: 7.7 +/- 0.6 mmol/kg dry wt) and increase in alanine concentration (posttraining: 3.3 +/- 0.2 vs. pretraining: 5.6 +/- 0.3 mmol/kg dry wt; P < 0.05), which is consistent with reduced carbon flux through alanine aminotransferase. We conclude that, after aerobic training, cycle endurance capacity is not limited by a decrease in muscle [TCAI].

Free amino acid pool and muscle protein balance after resistance exercise.

The aim of this study was to assess the effects of a resistance exercise session (RES) on free amino acid concentrations and protein synthesis and breakdown of the vastus lateralis (VL) muscle during recovery in male subjects. Both the exercise group (EG) and the control group (CG) consisted of six healthy physically active men. On the experiment day in fasting conditions, a stable isotopic tracer of L-[ring-2H(5)] phenylalanine was infused and EG started a heavy 50-min hypertrophic RES for lower extremities after 55 min of infusion. At the same time, CG was at rest. During recovery of 195 min after RES, several blood samples were drawn from the femoral artery (FA) and the femoral vein (FV) and muscle samples from the VL muscle. The enrichment was analyzed by GC/MS and leg muscle amino acid kinetics determined by three-pool compartment model between FA, FV, and VL. During recovery at 60 min after RES, there was no difference in muscle protein synthesis or muscle protein breakdown between the groups, but at 195 min, both muscle protein synthesis (P < 0.05) and muscle protein breakdown (P < 0.05) were increased in EG compared with CG. The protein net balance was negative and similar in both groups. Simultaneously in serum concentrations, there was a decrease in leucine (P < 0.05) associated with an increase in aspartate (P < 0.05). Furthermore, the exercise-induced increase in alanine concentration decreased both in serum and muscle. In fasting conditions, protein net balance is negative and RES induces an increase in muscle protein synthesis and breakdown at 195 min but not yet at 60 min of recovery.

Energy substrates for flight in the blister beetle Decapotoma lunata (Meloidae)

We investigated the substrates for flight in the blister beetle Decapotoma lunata by (a) establishing the patterns of maximum activities of enzymes of various metabolic pathways in the flight muscles, (b) measuring the respiratory rates of flight muscle mitochondria with various substrates and (c) determining metabolite concentrations in flight muscles and haemolymph during a flight period of up to 17 min and over a rest period of up to 2 h following 10 min of flight. Activities of enzymes involved in proline metabolism (glutamate dehydrogenase, alanine aminotransferase, malic enzyme) were much higher in the blister beetle than in the migratory locust Locusta migratoria, whereas the activity of an enzyme responsible for fatty acid oxidation (ss-hydroxyacyl-CoA dehydrogenase) was much lower. Mitochondria from flight muscles of D. lunata have a much higher capacity to oxidise proline than those from L. migratoria. The glycerophosphate shuttle, however, was equally active in both insects. Whereas lipid levels in the haemolymph did not change significantly during flight, there was a continuous decrease in proline levels from 34.8 to 6.6 micromol ml-1 and a simultaneous increase in alanine concentration; carbohydrate levels dropped from 20.1 to 12.2 mg ml-1. In the thorax (flight muscles), glycogen levels were diminished between 2 and 17 min of flight from 25.9 to 6.7 micromol glucose equivalents g-1 fresh mass. Proline concentration dropped continuously from an initial 49.5 to 10.1 micromol g-1 fresh mass, whereas alanine levels rose concomitantly from 2.9 to 17.3 micromol g-1 fresh mass. After termination of a 10 min flight, pre-flight levels of proline in the haemolymph and flight muscles were only re-established after 2 h. In contrast, glycogen levels in the thorax were restored after 1 h. Using the rates of utilisation of substrates during the first 10 min of flight to calculate rates of oxygen consumption during flight, it was shown that overall haemolymph substrates contribute 75 % and those of the flight muscles only 25 %. Although proline is an important substrate for flight in D. lunata, its role is secondary to that of carbohydrates. This type of substrate usage is different from that of the Colorado potato beetle Leptinotarsa decemlineata or the African fruit beetle Pachnoda sinuata, in which carbohydrates are of negligible or only slight importance, respectively.

Glutamine metabolism in the lungs of glucocorticoid-treated rats

1. The effect of dexamethasone (30 micrograms day-1 100 g-1 body weight) on the regulation of glutamine metabolism was studied in the lungs of rats after 9 days of treatment. 2. Dexamethasone resulted in a negative nitrogen balance, and produced decreases in the blood concentrations of glutamine (32.3%) and glutamate (25.3%) but an increase in the blood concentration of alanine (33.9%). 3. Dexamethasone treatment increases the rates of production of glutamine and alanine by lung slices incubated in vitro. 4. Blood flow and arteriovenous concentration difference measurement across the lungs exhibited an increase in the net exchange rates of glutamine (131.6%) and alanine (113.2%) in dexamethasone-treated rats compared with corresponding pair-fed controls. 5. Dexamethasone treatment produced significant decreases in the lung concentrations of glutamine (47.2%), glutamate (30.9%) and 2-oxoglutarate (57.3%). The concentrations of alanine (52.1%), ammonia (24.7%) and pyruvate (43.7%) were increased. 6. The maximal activity of glutamine synthetase was increased (21.5%), but there was no marked change in that of glutaminase, in the lungs of dexamethasone-treated rats. 7. It is concluded that glucocorticoid administration enhances the rates of production of glutamine and alanine from lungs of rats (both in vitro and in vivo). This may be due to changes in efflux and/or increased intracellular biosynthesis of glutamine and alanine.

Cerebral metabolic and circulatory effects of 1,1,1-trichloroethane, a neurotoxic industrial solvent. 2. Tissue concentrations of labile phosphates, glycolytic metabolites, citric acid cycle intermediates, amino acids, and cyclic nucleotides.

In order to obtain information on the mechanisms of neurotoxicity of 1,1,1-trichloroethane, rats maintained artificially ventilated on N2O:O2 (70:30) were exposed to a concentration of 1,1,1-trichloroethane of 8000 ppm, 43.7 mg L-1, that induces moderate ataxia in awake, spontaneously breathing animals. After 5 and 60 min of exposure, as well as after a 60-min recovery period following 60 min of exposure, the brain was frozen in situ and cortical tissue was assayed for phosphocreatine (PCr), + ATP, ADP, AMP, glycogen, glucose, pyruvate, lactate, citric acid cycle intermediates, associated amino acids, and cyclic nucleotides; in addition, purine nucleotides, nucleosides, and bases were assayed by HPLC techniques. Exposure of animals to 1,1,1-trichloroethane failed to alter blood glucose, lactate, and pyruvate concentrations. However, the solvent induced highly significant increases in tissue lactate and pyruvate concentrations that were also reflected in cisternal CSF. Associated with these changes were increases in all citric acid cycle intermediates except succinate, an increase in alanine concentration, and a rise in the glutamate/aspartate ratio. After 5 min, a small decrease in glycogen concentration also occurred. All these changes were reversed when the exposure was terminated. No changes were observed in tissue concentrations of purine nucleotides, nucleosides, and bases except for a small reduction of ATP concentration after 60 min of exposure, still noticeable after 60 min of recovery. Apart from a small reduction in cAMP concentration after 5 min of exposure, cyclic nucleotide concentrations did not change.

The Effect of X Irradiation on Amino Acid Utilization in Cultured Insect Cells

KOVAL, T. M., MYSER, W. C., AND HINK, W. F. The Effect of X Irradiation on Amino Acid Utilization in Cultured Insect Cells. Radiat. Res. 67, 305-313 (1976). Cultured Trichoplusia ni cells in exponential growth were administered X-ray doses of 10,000 R and then subcultured. The concentration of alanine increased greatly and ammonia increased slightly in media of both untreated and irradiated cells up to 96 hr. Glycine concentration did not change significantly while the concentration of the remaining amino acids decreased to varying extents in media from both irradiated and untreated cultures. It was assumed that a decreasing amino acid concentration in the growth medium was due to utilization of the amino acids by the cells while an increasing amino acid concentration reflected its production by the cells. In medium from both untreated and X-irradiated cultures, a decrease in glutamic acid concentration was proportional to an increase in alanine concentration. With time spent in culture, the amounts consumed and produced per cell were much higher in the irradiated cultures.

Changes in the cerebral metabolism induced by hyperventilation at different blood glucose levels.

Abstract—In order to study cerebral metabolism in hypocapnia, lightly anaesthetized rats were hyperventilated to PaCO2 about 15 mm Hg for 1, 2, 5 and 30min, the brain was frozen in situ, and cortical concentrations of organic phosphates, glycolytic and citric acid cycle metabolites, and amino acids were measured. In separate experiments, animals were made hypoglycaemic prior to induction of hypocapnia. Measurements of arteriovenous differences for oxygen and glucose indicated an increased glycolytic flux and the pattern of changes in glycolytic intermediates after 1 min suggested that this was due to an activation of the phosphofructokinase step.The pool size of citric acid cycle intermediates gradually increased with time of hypocapnia. This increase was, as in hypoxic hypoxia, related to the accumulation of pyruvate, probably via its effect on the alanine aminotransferase reaction and on the rate of CO2 fixation at the pyruvate carboxylase step. In hypoglycaemic, hypocapnic animals, in which the production of pyruvate was limited, the increase in pool size did not occur. It is suggested that the pyruvate concentration determines the net flux at the CO2 fixation step and thereby the direction of net flux of carbon skeletons between the citric acid cycle and the glycolytic chain. The changes in amino acids (glutamate, glutamine, alanine, GABA and aspartate) with time of hypocapnia were also similar to those occurring in hypoxic hypoxia. Thus, there was an increase in alanine concentration and a shift in aspartate aminotransferase reaction with increase in glutamate and fall in aspartate. It is suggested that the increase in alanine was secondary to a rise in pyruvate concentration, and that the shift in the aspartate aminotransferase reaction was due to reduction of the malate dehydrogenase system. This interpretation is supported by the fact that hypoglycaemia, by preventing a rise in pyruvate concentration and a reduction in the cytoplasmic redox system, also prevented the changes in amino acids.

Influence of anoxia on the energy metabolism of goldfish Carassius auratus (L.)

1. 1. Goldfish has a large anoxia tolerance. At 20°C 10 hr of complete anoxia can be survived without any problem. The concentration of some metabolites were determined in dependence of anoxia, both in whole fish and dorsal white muscle. 2. 2. Lactate production does not cover the energy need. 3. 3. Apart from an increase in lactate level we were able to demonstrate an increase in concentration of alanine, creatine, total CO 2 and ADP. 4. 4. Concentrations of ATP and creatine-phosphate decrease with anoxia while AMP, glutamate and volatile fatty acids did not change significantly. 5. 5. The “energy charge” in the white muscle falls during hypoxia from 1.0 till 0.8 and stabilizes at that level during about 10 hr although the direct energy reserves of ATP and creatine-phosphate decrease.

Salinity-induced changes in the alanine and aspartic aminotransferase activity in three marine bivalve molluscs.

Salinity-induced increase in alanine concentration of gill tissue of Mya arenaria and Spisula solidissima is correlated with increased alanine aminotransferase activity during the first day of osmotic stress due to salinity increase. Both responses are lacking in Mercenaria mercenaria. Metabolic pathways for alanine accumulation appear similar to those described for invertebrate facultative anaerobiosis.