End Products Of Protein Metabolism Research Articles

Direct and indirect cost of urea excretion

Urea, the major end product of protein metabolism in mammals, is the most abundant solute in the urine. Urea excretion is thought to result from filtration curtailed by some passive reabsorbtion along the nephron. This reabsorption is markedly enhanced by vasopressin and slow urinary flow rate (V), the fraction of filtered urea excreted in the urine (FEurea) falling from approximately 60% at high V to only approximately 20% at low V. In concentrated urine, normal urea excretion can be maintained only if urea filtration is elevated. This can be achieved by increasing plasma urea concentration (Purea) and/or GFR. We have shown that both parameters do increase when normal rats are submitted to chronic alterations in the water intake/vasopressin axis within the normal range of physiologic regulation. This situation is very similar to that observed after alterations in protein intake. In both cases more urea needs to be filtered, either because more of it has to be excreted, or because the efficiency of its excretion is reduced. A common mechanism is proposed to explain the rise in GFR observed in the two situations. In summary, our studies demonstrate that the antidiuretic effects of vasopressin are responsible for a significant elevation of GFR. This GFR adaptation limits the rise in Purea, a favorable effect because urea is not as harmless as usually thought. However, this hyperfiltration might have deleterious consequences in diseased kidneys.

Leukocyte endogenous mediator fails to alter protein dynamics in a model of liver dysfunction.

This study examines the effect of a purified leukocyte-derived endogenous mediator (LEM) on protein metabolism during liver dysfunction and after sham surgery and the role of a nonsteroidal, antiinflammatory drug (indomethacin sodium trihydrate) in modifying this response. Febrile response, protein kinetics, urinary end products of protein metabolism, and plasma acute phase protein levels were studied in rats given a pyrogenic dose of LEM or saline solution, and these same indicators were studied after the administration of the same dose of LEM plus 2 mg/kg indomethacin 3 weeks after a portacaval shunt (PCS) or sham operation. In both surgical groups given LEM, a maximum of 1.1 degrees C fever was observed. LEM increased protein turnover and urinary excretion of nitrogen and urea in sham-operated rats but not in the PCS animals. Administration of indomethacin decreased the plasma oxidation of L[1-14C]leucine and prevented the increased excretion of total nitrogen and urea in sham-operated animals treated with LEM. PCS animals showed a constant excretion of nitrogen and urea independent of treatment. alpha 1-Acid glycoprotein levels increased significantly in sham-operated animals treated with LEM but not in the PCS group until indomethacin was added. The coadministration of LEM and indomethacin in shams also enhanced the levels of alpha 2-macroglobulin and alpha 1-acid glycoprotein over values found with LEM alone. These findings confirm the catabolic effect of LEM in normal animals and identify the essential role of the liver in the acute phase response. The data also suggest that indomethacin may modify the acute phase response by reducing plasma amino acid oxidation as well as enhancing the levels of some specific acute phase proteins.

Influence of temperature and rate of feeding on nitrogen metabolism of juvenile bream ( Abramis brama L.)

1. 1. Measurements of the rate of nitrogen consumption, ammonia, urea and fecal nitrogen as well as total nitrogen excretion of fry of bream ( Abramis brama) (body weight range: 75–1400 mg wet wt) were made at 15 ± 1 and 20 ± 1° C. 2. 2. Fish were fed once daily on live Zooplankton at 10–15% of their body weight. 3. 3. Neither the temperature nor the ration size influenced the nitrogen consumption offish weighing less than 100 mg. However, food ration affected the nitrogen consumption rate of fish with body weight above 200 mg at 20°C. 4. 4. About 32–78% of the nitrogen consumed in food was excreted and its rate depended mainly on food consumption. 5. 5. Ammonia was the chief end product of protein metabolism; about 52–69% of the total excreted nitrogen was NH 4N. 6. 6. Temperature had no significant influence on its rate but food ration affected the ammonia excretion of fish fry. 7. 7. Urea made up 14–21% of the excreted nitrogen, depending slightly on temperature. 8. 8. The nitrogen content of feces was high and had a range between 20 and 23%.

Effect of Protein-Induced Calciuria on Calcium Metabolism and Bone Status in Adult Rats

45Ca-labeled adult male rats were fed diets high in protein to determine long-term effects on calcium metabolism and bone status. Factors influencing renal excretion of calcium were examined for their involvement in protein-induced hypercalciuria. Control rats were fed a 6% casein diet. Test diets contained 6% casein plus 24% protein as lactalbumin, beef, casein, soy, egg white or gelatin. All diets were equal in Mg, P, and Ca. Collections made during the 20-week feeding regimen indicated a transient but marked calciuria (≥200% of control) occurring at or prior to days 56–59 by rats fed the lactalbumin, egg white, gelatin (P ≤ 0.001) and 30% casein (P ≤ 0.01) diets. Soy and beef diets were not calciuric. At days 56–59, rats fed lactalbumin, 30% casein, soy and egg white exhibited significantly depressed urinary specific activity of calcium (P ≤ 0.001), and all rats fed test diets produced higher fecal endogenous calcium, suggesting an increased absorption. No compositional differences indicative of bone resorption were present in the femur or mandibles of any rat fed test protein, dismissing bone as the source of calciuria. End-products of protein metabolism known to chelate calcium or compete with its renal reabsorption were significantly correlated with urinary calcium; these included sulfate, oxalate and sodium.hypercalciuria protein calcium bone

Diurnal pattern of the ammonia and urea excretion of feeding and starved bream, Abramis brama L

1. 1. Measurements of the rate of ammonia, urea and total nitrogen excretion of young bream ( Abramis brama) were made (av. wt: from 8.1 ± 1.2−40.3 ± 6.3 g) at 15 ± 1 and 20 ± 1°C. 2. 2. Fish were fed daily on Zooplankton and Tubifex from 5–10% of their body weight. After completion of the experiments on feeding, fish measurements were carried out on bream starved for 30 days. Excreted ammonia and urea nitrogen were determined four times, while excreted total nitrogen once a day. 3. 3. About 50–60% of the nitrogen consumed with food was excreted as soluble compounds (NH 4-N, urea-N) and faecal nitrogen. 4. 4. Ammonia was the chief end product of protein metabolism as about 45–60% of the total excreted nitrogen was NH 4-N. 5. 5. Daily fluctuations in the proportion of ammonia excretion of feeding bream were observed, while urea showed a continuous rate of production. No diurnal response to feeding was observed. 6. 6. The daily pattern of ammonia excretion of starved bream fell in a manner comparable to the diurnal pulse of the 24 hr cycle of the feeding fish. The rate of urea excretion was also without any considerable changes during the starvation period.

Purine-nucleoside: orthophosphate ribosyltransferase activity in the hepatopancreas of Helix pomatia (Gastropoda)

1.1. Purine-nucleoside: orthophosphate ribosyltransferase (E.C. 2.4.2.1) activity was found in the hepatopancreas of the land snail, Helix pomatia (Gastropoda) during the active period and in hibernation.2.2. With our enzyme preparation inosine was the best substrate followed by guanosine and adenosine, while xanthosine and uridine were not cleaved.3.3.The enzyme properties resembled those of the chicken liver enzyme, but no inhibition by ADP and Na2SO4 was observed.4.4. Ribosyltransferase is postulated to participate in the pathway leading from IMP to xanthine and uric acid—the end-products of protein metabolism in H. pomatia. Phosphoribosyltransferase (E.C. 2.4.2.8) and ribohydrolase (E.C. 3.2.2.1) catabolic activities were not found in the same preparations.

Determination of Uric Acid in Avian Excreta by the Use of Uricase and Differential Spectrophotometry

STUDIES on protein metabolism are often handicapped in the avian species because urine and feces are voided together. Since approximately 80% of the urinary nitrogen of the chick is present as uric acid (O’Dell et al., 1960), a simple, reliable method for the determination of this end product of protein metabolism in the chick would be desirable.Colorimetric methods for the determination of uric acid in urine and blood have largely been replaced by combining enzymatic with spectrophotometric methods (Kalckar, 1947); however, this combination has not been used for uric acid determinations in poultry excreta.Bose and Ghosh (1945) determined the uric acid content of poultry excreta by utilizing the difference in iodine titer before and after treatment with uricase. Buys and Potgieter (1959) used a spectrophotometric method but ruled out the use of uricase because of a reported inhibition (up to 95%) of the enzyme by xanthine (van Pilsum, .

Main excretory end-products of protein and purine metabolism in lizards and snakes

1. Uric acid is the main nitrogenous constituent of the urinary excreta of a group of lizards and snakes forming 54.55% to 67.51% of the total excretory nitrogen. 2. Excretion of the insoluble uric acid as a main nitrogenous end product helps these animals for water conservation as they live under xerophilous conditions of low water intake. 3. Allantoin is present in the urinary concretions of lizards and absent from that of snakes. 4. Uric acid represents the end product of protein metabolism, and in lizards, allantoin should be a accepted as representing the line of purine metabolism.

Serum Urea Concentrations

From a historical viewpoint, urea is the first organic compound to have been synthesized by man in vitro; physiologically, by contrast, urea is the last one to be formed by him in vivo after a protein meal. Thus in the mammal, urea is the chief end product of protein metabolism, comprising some 80% of the non-protein nitrogen normally excreted in the urine per 24 hours. 1 Urea is generated in the liver as the end product of the activity of the first enzymatic cycle to have been described by Krebs, the ornithine-arginine-urea cycle. 2 Amino acids, derived from dietary protein or from peripheral tissues, consequent to the interchange of serum (dietary) and tissue amino acids, serve as the precursors fed into the enzymatic degradation process. The rate of urea formation is determined by the quantity of amino acids presented to the liver per unit of time. Accordingly, urea synthesis is

Serum urea concentrations

From a historical viewpoint, urea is the first organic compound to have been synthesized by man in vitro; physiologically, by contrast, urea is the "last" one to be formed by him in vivo after a protein meal. Thus in the mammal, urea is the chief end product of protein metabolism, comprising some 80% of the non-protein nitrogen normally excreted in the urine per 24 hours.¹ Urea is generated in the liver as the end product of the activity of the first enzymatic cycle to have been described by Krebs, the ornithine-arginine-urea cycle.²Amino acids, derived from dietary protein or from peripheral tissues, consequent to the interchange of serum (dietary) and tissue amino acids, serve as the precursors fed into the enzymatic "degradation" process. The rate of urea formation is determined by the quantity of amino acids presented to the liver per unit of time. Accordingly, urea synthesis is

Renal Function and Renal Failure—A Programmed Text.

This book is intended to complement the one on Renal Function and Renal Failure by Dr. Bernstein. The authors have organized in a clear, deductive way all the material presented in the original book. The text opens with a statement concerning kidney function in regard to the excretion of the end products of protein metabolism and its direct relationship to the number of functioning nephrons. The analogy is made of a container with a constant rate of input in which the fluid level is balanced through a set of spigots in the bottom, and renal failure is compared to the progressive shutting off of the spigots. Three or four alternatives are given as possible correct answers to each question. Having chosen one, the reader is instructed to turn to a discussion of his selection. If his answer is wrong, he is told why and returns to the question to select

Nitrogenous Excretion in Arachnids

ANIMALS are known to excrete ammonia, urea, or uric acid as end-products of protein metabolism. So far as we can ascertain, the problem of nitrogenous excretion in arachnids needs more investigation. Since the work of Gorup-Besanez and Will1 in 1849, guanine was regarded as taking the place of uric acid as the main nitrogenous end-metabolite in arachnids. The method of synthesis of guanine in these animals is unknown2.

Some Physiological Studies on Growth and Feed Efficiency of Beef Cattle

INTEREST at Oregon State University has been concerned with the physiological mechanism by which inherited differences bring about differences in growth rate and efficiency. When this research was initiated, physiological differences that could logically be expected to have some influence were: (1) differences in appetite in which animals that consume more feed grow more rapidly and efficiently, (2) differences in ability to digest the feed eaten, (3) differences in storage products with more rapidly growing animals storing more protein, (4) differences in metabolism such that some animals can convert the feed eaten into growth with greater efficiency than others. Because information is difficult to obtain on ruminants in a post adsorptive state, studies on precursors and end products of metabolism in the blood and urine seem appropriate.The present study is concerned with certain precursors and end products of protein metabolism in growing beef cattle that differ markedly in growth rate and efficiency of converting feed into body gains.

Studies of Serum and Egg Yolk Cholesterol Level of Hens Immunized Against Newcastle Disease

Abstract In studies of biochemical patterns in blood, Agarwal (1956) observed an increase in plasma iron and a reduction of blood cholesterol, but little change in the end products of protein metabolism following experimentally induced rabies in sheep. Similar results were reported by Mondini (1955) in horses hyperimmunized against tetanus toxin. Contrary to these reports, Puntigam and Berger (1955), investigating serum cholesterol levels of healthy heifers used for the production of smallpox vaccine, observed that, within four days following inoculation, the esterified cholesterol rose by approximately 16 percent in two-thirds of the animals. Then a gradual drop in cholesterol level occurred and, between the 10th and 14th day after inoculation, a minimum value of 40 percent of the initial level was reached. Free cholesterol was affected similarly. Owing to the importance of cholesterol in many body functions and, in view of the frequency with which vaccination is used in modern prophylaxis…

An investigation of the effects of irradiation on serum leucine aminopeptidase (LAP).

The presence of a circulating proteolytic enzyme acting upon the end-products of protein metabolism has been known for many years. In 1929 an enzymatic dipeptide acting directly on L-leucylglycine was identified and named leucine aminopeptidase. This enzyme has not yet been isolated in its pure state, but can be assayed in serum and urine by a colorimetric determination (2). Leucine aminopeptidase (LAP) is found in all human tissue, with highest concentrations in the liver, biliary tract, and duodenal mucosa. Although there have been considerable investigation and documentation of the biochemical and physical properties of the enzyme, its specific function in the blood remains unknown (1). Since leucine aminopeptidase is excreted by the liver into the bile, obstructions in the biliary tract result in elevated serum levels of the enzyme. Attempts have been made to determine whether increases in the blood can be interpreted as evidence of biliary or pancreatic disease when clinical manifestations such as jaundice are absent. Rutenburg et al. (1958) claimed that the degree and duration of serum LAP elevations in jaundiced patients helped distinguish between carcinoma of the pancreas and other icteric conditions (6). Other authors contend that the LAP test merely denotes obstructive disease in the biliary tract, without reference to the cause of obstruction (4, 7). Persistently high LAP readings have been noted in the following conditions: carcinoma involving the head and, to a lesser extent, the tail of the pancreas; carcinoma of the gallbladder and biliary tree ; choledocholithiasis; inflammatory disease of the biliary tract; primary liver disease, such as infectious mononucleosis and infectious hepatitis; remote cancer metastatic to the liver (3, 4, 5). Serum LAP is not ordinarily elevated in patients with malignant disease unrelated to the hepato-biliary-pancreatic system, although high readings are occasionally obtained. Transient LAP elevations are noted in the third trimester of pregnancy and in the immediate postoperative state (8). Of special interest is the evidence that a markedly elevated LAP in an anicteric patient with cancer suggests metastatic deposits in the liver (4). Corroboration of this contention would provide the clinician with a simple test to help evaluate a course of treatment for the patient with malignant disease. Since LAP is a proteolytic enzyme, a nonspecific elevation may occur as a reflection of tissue destruction in areas remote from the hepato-biliary system. Injury to hepatic cells has been shown to result in extravasation of the enzyme into the circulation, with a subsequent rise in the serum concentration (5). The elevation in serum LAP following surgery may be equated to the degree of tissue trauma during the procedure. Controlled, localized tissue injury is inherent in radiation therapy of malignant disease.

Nitrogen Retention and Nitrogenous Urine Components of Growing Cockerels as Influenced by Diethylstilbestrol, Methyl Testosterone and Porcine Growth Hormone

Abstract THE mechanism by which a rapidly growing animal retains nitrogen and accumulates body protein, and the role of the endocrine system in this regard has intrigued investigators for many years. An indirect method of studying protein metabolism is to study changes induced in the excretory pattern of the end products of protein metabolism, namely, nitrogenous waste products. Attempts to investigate, in detail, the metabolism of chickens are met with the primary difficulty of separately collecting feces and urine for subsequent analysis. Metabolism studies with chickens have therefore been hampered greatly and little research has been done beyond collecting data on gross nitrogen retention. Consequently, little data on nitrogenous urine components of growing chickens under what might be considered normal conditions or under the influence of various treatments (dietary, hormonal or other) are available. Among the early workers who collected data on nitrogenous components in the urine of the chicken were…

Observations on the end products of protein metabolism in diploid and tetraploid Artemia salina (Leach)

Ammonia elimination of nauplii and metanauplii stages has been studied in diploid and tetraploid biotypes of Artemia salina Leach.Ammonia production is lower in diploid Artemia; in connection with these results, some data previously obtained on the enzymatic activities of the two biotypes in Artemia have been referred to, and it has been underlined that in tetraploid individuals the stronger ammonia elimination is accompanied by a stronger dipeptidase activity.

NITROGEN EXCRETION IN SOME MARINE TELEOSTS

The nitrogen-containing compounds excreted by the sculpin, starry flounder, and blue sea-perch were investigated. Approximately four-fifths of the nitrogenous material was excreted via the gills. Ammonia and urea were the main components of the excreta in all three species. The amount excreted in 24 hours varied greatly between fish of any one species, but the percentage composition was reasonably constant. A greater variation in the composition occurred between species. Trimethylamine oxide was present in only small amounts in the total excreta. It was concluded from this that the compound was not an important end product of protein metabolism.

NITROGEN EXCRETION IN SOME MARINE TELEOSTS

The nitrogen-containing compounds excreted by the sculpin, starry flounder, and blue sea-perch were investigated. Approximately four-fifths of the nitrogenous material was excreted via the gills. Ammonia and urea were the main components of the excreta in all three species. The amount excreted in 24 hours varied greatly between fish of any one species, but the percentage composition was reasonably constant. A greater variation in the composition occurred between species. Trimethylamine oxide was present in only small amounts in the total excreta. It was concluded from this that the compound was not an important end product of protein metabolism.

ARTERIOSCLEROSIS AND INCREASED BLOOD PRESSURE

There is a great diversity of opinion concerning the etiologic factors of increased blood pressure and arteriosclerosis. The frequent association of the two conditions is granted. Which precedes the other, and what precedes both, have been matters of much study and debate. Five theories regarding the etiology of arteriosclerosis and hypertension may be considered: Mechanical-physical theory. A wearing out of the blood vessels as the result of the stress and strain of life. Chemical or infectious poisons theory. These may be exogenous, as from nicotine, or endogenous, as in chronic bacterial infections, diabetes, gout and nephritis. Metabolic theory. Poorly balanced diets with excess of protein or cholesterol; harmful but as yet undesignated end products of protein metabolism. Predisposition of certain groups of persons to degeneration of blood vessels theory. Disturbance of the acid-base balance theory. Such a disturbance in human subjects results from the continued eating of a diet