Amino-acid metabolism enzyme activities in the liver, intestine and yolk sac membrane of developing domestic fowl

To contribute to our understanding of nitrogen metabolism in the developing chick we have studied in liver, intestine and yolk sac membrane the ontogeny of both aspartate- and alanine transaminases, glutamate dehydrogenase, adenylate deaminase, glutamine synthetase and xanthine dehydrogenase activities. Liver enzyme activities were much higher than those of the same enzymes in intestine and yolk sac membrane, the latter having the lowest activities. In the liver, both alanine transaminase and glutamate dehydrogenase increased their activity just before hatching, xanthine dehydrogenase and glutamine synthetase develop their highest activity just after hatching, while aspartate transaminase and adenylate deaminase attained the highest levels just with adulthood. From the pattern of enzyme activity in yolk sac membrane and intestine it can be inferred that after hatching, the amino-acid metabolism in these tissues is considerably enhanced, with higher production of ammonia from amino acids, as indicated by the rise in adenylate deaminase, as well as increased potentiality in production of both alanine and glutamine. It can be concluded that hatching coincides with a deep change of pace in amino-acid metabolism in the organs studied fully comparable with that observed in Mammals at the end of lactation, with the difference that the adaptation to the new diet in the case of the chick is much more sudden than weaning is for the rat.     

Glutamine and ammonium handling by anaesthetized rats

The infusion of ether anesthaetized rats with 0.2 M (1 mmols in total) ammonium acetate or glutamine were compared with the infusion of 0.2 M NaCl. The levels of circulating glucose, amino acids, lactate, urea and ammonium were measured as well as liver glycogen and tissue amino acids and the liver and muscle activities of carbamoyl phosphate synthetases I and II, glutamate dehydrogenase, glutamine synthetase and adenylate deaminase. Neither treatment altered the glucose and glycogen homeostasis. The infusion of ammonium did not result in increases in circulating ammonium, but resulted in increased circulating urea after a short delay; the infusion of glutamine resulted also in urea production but much later on. Glutamine infusion also resulted in increased tissue free amino-acid levels. There was little alteration in enzyme activities, except for decreased glutamine synthetase and adenylate deaminase activity in muscle of glutamine-infused rats and higher tissue carbamoyl phosphate synthetase II. The results agree with a fast removal of infused ammonium, and maintenance of glutamine, with their channeling towards urea production at a rate comparable with that of infusion, that did not alter significantly the homeostasis of the experimental animals.     

Effect of starvation and a protein diet on the amino acid metabolism enzyme activities of the organs of domestic fowl hatchlings

The activities of alanine and aspartate transaminases, adenylate deaminase, glutamine synthetase and glutamate and xanthine dehydrogenases have been measured in liver, yolk sac membrane, intestine and breast and leg muscle of domestic fowl hatchlings receiving for 3 or 5 days either a standard diet or hard boiled eggwhite as well as in 3 or 5 days starved animals. The patterns of activation of amino acid metabolism enzymes were fully comparable in protein-fed and starved groups with respect to fed controls; the differences with respect to the latter became more marked in 5- than in 3-days old chicks. In 5-days old chicks intestine alanine transaminase activity increased in parallel to that of liver in protein-fed animals but not in those starved, in agreement with an enhanced alanine transfer between both organs under this situation. Both, starvation and protein-feeding, induced a general decrease in the amino acid metabolizing ability of muscle. Glutamine (but not alanine) synthetizing capabilities were enhanced.     

Distribution of amino acids and amino-acid enzymes in whole kidney and renal cortex. Effect of 24-h starvation

The levels of activity of amino-acid enzymes (alanine-, aspartate- and tyrosine transaminases, serine dehydratase, glutamate dehydrogenase, glutamine synthetase, arginase and adenylate deaminase) in the kidney cortex and whole kidney of control and 24-h starved adult rats have been determined from crude homogenates. The individual amino-acid content of the two kidney fractions indicated has also been studied. Serine dehydratase was found mainly in the cortex, whilst glutamine synthetase presence was mainly limited to the medulla. The distribution of adenylate deaminase and glutamate dehydrogenase is remarkably uniform along the kidney. Starvation induced decreases in arginase and adenylate deaminase activities as well as a decrease in cortical serine dehydratase. Analysis of the variance of the enzyme data showed no significant overall changes with respect to distribution and starvation. The same analysis applied to aminograms indicated only significant changes when the distribution was studied on starved samples as a whole, with changes mainly in the urea cycle and some essential amino acids. The results suggested a remarkable degree of uniformity in kidney composition both with respect to amino acid and enzyme distribution. This uniformity is not markedly affected by starvation despite the important r?le of kidney in the overall amino-acid economy of the Mammal.     

Activities of enzymes of amino acid metabolism in rat brown adipose tissue

There was a nil arginase and serine dehydratase activities in interscapular brown adipose tissue, but the activity of adenylate deaminase, glutamine synthetase, glutamate dehydrogenase and the aspartate, alanine and branched chain amino acid transaminases was higher than those of white adipose tissue; the differences were diminished when expressed per unit of protein weight. Brown adipose tissue enzyme activities were in a range between those of liver and muscle. The high amino acid handling capabilities, together with its physiological role, suggest that brown adipose tissue can metabolize significant amounts of amino acids, its enzyme pattern being different both from white adipose tissue, as well as of liver and muscle.     

Amino-acid metabolism enzyme activities in rat white adipose tissue

The activities of alanine-, aspartate- and branched-chain amino-acid transaminases, glutamine synthetase, glutamate dehydrogenase and adenylate deaminase in white adipose tissue of adult male rats have been determined in animals submitted to 12-h cold exposure (4 degrees C) or to 24-h food deprivation. Starvation resulted in small changes in glutamate dehydrogenase and alanine transaminase when expressed per unit of protein weight, inducing an increase in branched-chain amino-acid transaminase and glutamine synthetase. Cold exposure showed the same effects as starvation with respect to glutamate dehydrogenase and alanine transaminase, but induced increases in glutamine synthetase and aspartate transaminase. It is concluded that starvation increases the handling of some amino acids by white adipose tissue and the detoxification of the ammonia thus evolved. The changes observed suggest a different pattern of amino-acid metabolism enzyme changes with either cold or starvation.     

Ontogeny of amino-acid metabolism-enzymes in peripheral tissues of developing rats

The activities of alanine, aspartate and tyrosine transaminase, adenylate deaminase, glutamate dehydrogenase and glutamine synthetase have been measured in hind leg striated muscle, lumbar adipose tissue and lumbar skin of developing rats from late foetal to weaning stage. In a general way, despite minor differences and different physiological r?les, the three peripheral tissues studied showed a concordant enzyme activity pattern with the r?les found for these enzymes in the adult. Muscle had a more constant pattern throughout development, with wider changes in skin and widest in adipose tissue. The results found agree with a marked "synthetic" mode in the tissues studied throughout all development studied. The patterns observed agree with a strict amino-acid conservation scheme during foetal life and lactation that progressively changes with weaning towards a frank degrading mode.     

Activities of enzymes involved in amino-acid metabolism in developing rat placenta

Aspartate transaminase, alanine transaminase, glutamate dehydrogenase, arginase, serine dehydratase, tyrosine transaminase, glutamine synthetase, glutaminase and adenylate deaminase activities were measured in crude homogenates of 12, 19 and 21-day rat placentae. There is a considerable quantitative importance in enzymes able to produce free ammonia, such as adenylate deaminase and glutamate dehydrogenase, activity that progressively decrease with the age of placenta. The glutamine synthetase and tyrosine transaminase activities increase with age, while serine dehydratase decreases considerably and aspartate and alanine transaminase do not change practically. Arginase shows a maximum at 19, with lower 12 and 21-day activities. No measurable glutaminase activity has been found. The possible implications of the enzymes studied upon the ammonia-producing activity of rat placenta are discussed together with the relative decreasing role of placenta for the overall metabolic activity of the foetus, especially during the last phases of its development.     

Tissue glycogen and lactate handling by the developing domestic fowl

The levels of glycogen and lactate in liver, intestine, yolk sac membrane and leg and breast muscle of domestic fowl from day 10 of "in ovo" development to day 5 after hatching compared with adults have been measured and compared with the circulating concentrations in blood of glucose and lactate. Glycogen stores in most tissues increased before hatching to attain a minimum around the eclosion and then increased to adult values in muscle and liver. Lactate maintained its plasma concentrations with higher effectiveness than plasma glucose, which increased steadily up to adult levels from hatching. The study of tissue vs plasma lactate concentration ratios suggests a general activation of lactate metabolism from hatching, coinciding with the ingestion of carbohydrate-based food. Both muscles studied, as well as intestine, seem to be net lactate producers; blood cells can speculatively be considered as lactate users and liver maintains its concentration of lactate very close to that of plasma, suggesting a fast utilization of this material as well as liver being the main site for control of circulating lactate.     

Tissue glycogen and lactate handling by the developing domestic fowl

The levels of glycogen and lactate in liver, intestine, yolk sac membrane and leg and breast muscle of domestic fowl from day 10 of "in ovo" development to day 5 after hatching compared with adults have been measured and compared with the circulating concentrations in blood of glucose and lactate. Glycogen stores in most tissues increased before hatching to attain a minimum around the eclosion and then increased to adult values in muscle and liver. Lactate maintained its plasma concentrations with higher effectiveness than plasma glucose, which increased steadily up to adult levels from hatching. The study of tissue vs plasma lactate concentration ratios suggests a general activation of lactate metabolism from hatching, coinciding with the ingestion of carbohydrate-based food. Both muscles studied, as well as intestine, seem to be net lactate producers; blood cells can speculatively be considered as lactate users and liver maintains its concentration of lactate very close to that plasma, suggesting a fast utilization of this material as well as liver being the main site for control of circulating lactate.     

Influence of cold exposure on liver amino acid metabolism enzymes of the rat

The activities of alanine, aspartate and branched-chain amino acid transaminases, glutamate dehydrogenase, glutamine synthetase and adenylate deaminase have been studied in liver of male rats exposed [12 hours at 4 degrees C] or acclimated [15 days at 4 degrees C] to cold temperature. Cold temperature induced an increase of the activities of glutamate dehydrogenase and alanine and aspartate transaminases both in cold-exposed and cold-acclimated animals; adenylate deaminase activity diminished after 15-day cold acclimation. There were not significant changes induced by cold temperature in the activities of the other two enzymes studied. These results agree with a possible direct implication of amino acid utilization by the liver in the context of the overall thermogenic response to cold temperature.     

Effect of diet and essential amino acids gavage on young rat amino acid metabolism enzymes

• 1.1. The effects of a high-fat, high-energy diet and essential plus semi-essential amino acid gavage on pup rats have been studied (60–65 animals).
• 2.2. The activities of alanine transaminase, adenylate deaminase, glutamine synthetase and serine dehydratase have been tested in liver and muscle.
• 3.3. Plasma was used for the estimation of proteins, urea, amino acids, glucose, lactate, 3-hydroxy-butyrate and acetoacetate.
• 4.4. Liver and muscle glutamine synthetase activities are increased by diet and gavage administered. Hepatic serine dehydratase is inhibited by a cafeteria diet but activated by amino acid gavage. Adenylate deaminase is inhibited by diet and gavage in the liver, but gavage does not affect this enzyme activity in muscle. Liver alanine transaminase is increased by the diet; in the muscle, cafeteria diet and amino acid gavage showed the highest values for this enzyme.
• 5.5. In the plasma, the increase in lactate produced by the diet is inhibited by the amino acids provided. Cafeteria-fed pups showed lower urea levels and higher 3-hydroxybutyrate concentrations in the plasma.
• 6.6. Intracellular glucose is diminished by cafeteria diet. In contrast, the blood cell amino acid concentration increases with diet and gavage supplied.

     

Amino-acid enzyme activities in liver and kidney of developing rats

The amino-acid enzymes (aspartate-, alanine- and tyrosine transaminases, serine dehydratase, glutamate dehydrogenase, glutamine synthetase, adenylate deaminase and arginase) activities in the liver and kidney of developing rats (days 19 and 21 after conception and 1, 5, 10, 20 and 30 after birth) compared with adults were determined in crude homogenates. Most enzymes attained the adult levels early after birth or at weaning, showing a marked trend towards amino-acid nitrogen conservation during late foetal and specially during the neonatal period, increasing their activity during lactation. It is postulated that these changes are closely related to availability of low grade protein in diet as well as to maturation of amino-acid homeostasis maintenance for growth.     

Age-related changes in the incorporation of [14-C] leucine into myofibrillar and sarcoplasmic proteins of red and white muscles of chicks.

Studies on the incorporation of DL-[1- 14-C] leucine into myosin, total myofibrillar protein and total sarcoplasmic protein have shown age-dependent alterations in the rate of synthesis of these protiens in red and white skeletal muscles of chicks. During the early phase of ex ovo development white muscle synthesizes significantly higher amounts of myofibrillar proteins, especially myosin, in comparison with red muscle. The rate of sarcoplasmic protein synthesis in red and white muscles one day after hatching is almost identical. The red muscle shows a markedly higher rate of sarcoplasmic protein synthesis from 10 days after hatching. The incorporation of amino acid into various protein fractions of both the muscle types decreases with advancing age. In adult chicks red muscle displays a higher ability to synthesize sarcoplasmic and myofibrillar proteins.     

Effect of cold-temperature exposure and acclimation on amino acid pool changes and enzyme activities of rat brown adipose tissue

The amino acid pool composition and its concentration ratios with respect to blood and plasma, as well as the activities of alanine, aspartate and branched chain amino acid transaminases, glutamine synthetase, adenylate deaminase and glutamate dehydrogenase have been studied in the interscapular brown adipose tissue of control, 12-h cold-exposed and 15-day cold-acclimated rats. Cold temperature affected the amino acid metabolism and pool composition more intensely after 15 days than after 12-h cold-exposure, even though the patterns of change were very similar in both groups. Cold temperatures induced a decrease in glutamine and an increase in glutamate concentration in the tissue. This probably increased the metabolism of branched chain amino acids and caused a decrease in adenylate deaminase activity. It also seemed to increase alanine utilization. We concluded that amino acid metabolism in brown adipose tissue is enhanced by cold temperature acclimation.     

Effect of 24-hour starvation on amino acid pool composition and enzyme activities of rat brown adipose tissue

The effect of 24-hr starvation on the amino acid pool composition and its concentration ratios with respect to blood and plasma as well as the activities of alanine, aspartate and branched chain amino acid transaminases, glutamate dehydrogenase, glutamine synthetase and adenylate deaminase have been studied in rat brown adipose tissue. Starvation induced a considerable decrease of pool amino acid concentration. Alanine and taurine were the amino acids in which the decrease was more marked. Small changes were observed in the activities of the enzymes studied, with decreases only in glutamate dehydrogenase and adenylate deaminase. These changes agree with a decrease in amino acid utilization in this tissue induced by starvation.     

Metabolic adaptations to nitrogen excess in late gestation in rat.

Pregnant rats of 19th and 21st days were given an acute nitrogen overload produced by an infusion of either 0.2 M ammonium acetate or 0.2 M glutamine. Metabolic adaptations to nitrogen excess were studied measuring--in fetomaternal unit--non-protein nitrogen content and the activities of enzymes related with ammonia metabolism. Maternal and fetal plasma urea levels were increased by ammonium acetate treatment. Glutamine overload increased more the amino acid content in the mothers than in conceptus. As response to ammonium acetate treatment, glutamate dehydrogenase activity in liver was more sensitive in pregnant than in nonpregnant rats, suggesting more nitrogen incorporation into amino acids in pregnancy. Regarding glutamine synthetase activity, both treatments had an opposite effect except in kidney. The adenylate deaminase activity of pregnant rats was inhibited similarly to nonpregnant rats by nitrogen overloads, but stronger after glutamine infusion. Placenta and fetal metabolism were adjusted, as the dams, to lack of ammonia production by nitrogen overloads and to glutamine synthesis by ammonium acetate infusion.     

Myosin light-chain expression during avian muscle development

Monoclonal antibodies to adult chicken myosin light chains were generated and used to quantitate the types of myosin light-chain (MLC) isoforms expressed during development of the pectoralis major (PM), anterior latissimus dorsi (ALD), and medial adductor (MA) muscles of the chicken. These are muscles which, in the adult, are composed predominantly of fast, slow, and a mixture of fiber types, respectively. Three distinct phases of MLC expression characterized the development of the PM and MA muscles. The first identifiable pase occurred during the period of 5-7 d of incubation in ovo. Extracts of muscles from the pectoral region (which included the presumptive PM muscle) contained only fast MLC isoforms. This period of exclusive fast light-chain synthesis was followed by a phase (8- 12 d of incubation in ovo) in which coexpression of both fast and slow MLC isoforms was apparent in both PM and MA muscles. During the period, the composition of both fast and slow MLC isoforms in the PM and MA muscles was identical. Beginning at day 12 in ovo, the ALD was also subjected to immunochemical analyses. The proportion of fast and slow MLCs in this muscle at day 12 was similar to that present in the other muscles studied. The third development phase of MLC expression began at approximately 12 d of incubation in ovo and encompassed the transition in MLC composition to the isoform patterns incubation in ovo and encompassed the transition in MLC composition to the isoform patterns typical of adult muscle. During this period, the relative proportion of slow MLC rose in both the MA and ALD and fell in the PM. By day 16, the third fast light chain, LC(3f), was apparent in extracts of both the PM and MA. These results show that there is a developmental progression in the expression of MLC in the two avian muscles studied from day 5 in ovo; first, only fast MLCs are accumulated, then both fast and slow MLC isoforms are expressed. Only during the latter third of development in ovo is the final MLC isoform pattern characteristic of a particular muscle type expressed.     

Metabolic alterations in the red and white muscles of rat to acute ethanol treatment

Lactate (LDH) and succinate (SDH) dehydrogenases activities decreased in red and white muscles of rat under acute ethanol loading indicating the inhibition of energy metabolism and stepped up lactic acid formation under stress conditions. Aspartate aminotransferase (AAT) and glutamate dehydrogenase (GDH) were found to increase. In contrast to these, the AMP deaminase activity decreased in white muscle suggestive of decreased deamination of nucleic acids. The ornithine cycle enzymes such as argininosuccinate synthetase (ArSS) and arginase indicated diminished activities showing low level of operation of urea cycle and consequent accumulation of ammonia was observed in red muscle with low production of glutamine, whereas in the case of white muscle this trend is reversed. The possible alterations of ethanol toxicity on energy requirements, transdeamination patterns, ureogenesis and glutamine production have been discussed.     

Ontogenic expression of the two isozymes, Ch1 and Ch2, of chicken muscle acylphosphatase

Activities of the two isozymes, Ch1 and Ch2, of chicken muscle acylphosphatase were measured in breast muscles, leg muscles, and livers of developing chicks from day 11 in ovo to day 15 of free life. Measurement was performed using rabbit antibodies which could selectively precipitate Ch1 or Ch2. The activity contents of both Ch1 and Ch2 in muscles were low before hatching but rapidly increased after hatching. Ch1 showed a more marked increase than Ch2. In liver, on the other hand, the activity contents of Ch1 and Ch2 remained low throughout the period of pre- and post-hatching.