Proteins Metabolism, Liver

FIGURE 23.25 The effects of cortisol on carbohydrate and protein metabolism in the liver. 

Phosphorylation Glycogen Metabolic Movements of Glycogen Fat Metabolic Movements of Fat Protein Metabolic Movements of Protein Tissue Cooperation Liver Muscle Ketone Bodies... 

Hydrocephaly decreases in weight of brain, lung, liver, and kidney decreases in liver glycogen, kidney proteins and alkaline phosphatase and disrupted brain DNA and protein metabolism (Kav-lock et al. 1982)... 

Absorption/Distribution - Pyrazinamide is well absorbed from the Gl tract and attains peak plasma concentrations within 2 hours. It is widely distributed in body tissues and fluids including the liver, lungs, and cerebrospinal fluid. Pyrizinamide is approximately 10% bound to plasma proteins. Metabolism/Excretion - The half-life is 9 to 10 hours it may be prolonged in patients with impaired renal or hepatic function. 

Pharmacokinetics Rapidly absorbed after PO administration. Weakly bound to plasma proteins. Metabolized in the liver. Excreted in urine. Half-life 5-6 hr. 

Mechanism of Action An antiplatelet that directly dilates pulmonary and systemic arterial vascular beds, inhibiting platelet aggregation. Therapeutic Effect Reduces symptoms of pulmonary arterial hypertension associated with exercise. Pharmacokinetics Rapidly, completely absorbed after subcutaneous infusion 91% bound to plasma protein. Metabolized by the liver. Excreted mainly in the urine with a lesser amount eliminated in the feces. Half-life 2-4 hr... 

Disorder of protein metabolism could be noticed in 13% decrease of total protein content in blood serum. The observed hypoproteinemia was stipulated by 25% decrease of albumin fraction. The index showing correlation between the level of middle molecules and total protein was 65% higher in Group 2 indicating prevalence of protein degradation processes over their synthesis. The revealed disorders indicated the development of liver failure syndrome. Profound disorders were also registered in lipid metabolism. We determined the intensification of lipolysis by increase in the concentration of the main lipid fractions in blood serum. The level... 

The mammalian liver is a construction of living cells that function (unlike in other organs) in a delicate choreography that simultaneously detoxifies, metabolizes, and synthesizes proteins. The liver handles the breakdown and synthesis of carbohydrates, lipids, amino acids, proteins, nucleic acids, and coenzymes (Figure 1.8). In addition to the hepatocytes, other cells within the liver perform other vital functions. The system contributes to the disposition of particulates carried by the bloodstream and fights myriad microbiological agents responsible for a number of infectious diseases. ... 

Miller, L. L., John, D. W. Nutritional, hormonal, and temporal factors regulating net plasma protein biosynthesis in the isolated perfused rat liver. In Plasma protein metabolism, pp. 207. Rothschild, M. A., Waldmann, T. (eds.). New York, London Academic Press 1970... 

Effects on protein metabolism Glucagon increases uptake of amino acids by the liver, resulting in increased availability of carbon skeletons for gluconeogenesis. As a consequence, plasma levels of amino acids are decreased. 

Major metabolic pathways in liver in the absorptive state. [Note The numbers in circles, which appear both on the figure and in the text, indicate important pathways for carbohydrate, fat, or protein metabolism.]... 

Proteolytic enzymes such as proteases and peptidases are ubiquitous throughout the body. Sites capable of extensive peptide and protein metabolism are not only limited to the liver, kidneys, and gastrointestinal tissue, but also include the blood and vascular endothelium as well as other organs and tissues. As proteases and peptidases are also located within cells, intracellular uptake is per se more an elimination rather than a distribution process [13]. While peptidases and proteases in the gastrointestinal tract and in lysosomes are relatively unspecific, soluble peptidases in the interstitial space and exopeptidases on the cell surface have a higher selectivity and determine the specific metabolism pattern of an organ. The proteolytic activity of subcutaneous tissue, for example, results in a partial loss of activity of SC compared to IV administered interferon-y. 

Table 2.2 Changes in protein metabolism and degradation seen in liver disease...

The aflatoxins are a group of related mycotoxins produced by the mould Aspergillus flavus. There are four toxins, B, B2, G, and G2. The mould typically grows on crops such as grain and peanuts in hot, humid climates. There is evidence from epidemiology of an association between exposure to aflatoxin Bi in the diet and liver cancer in humans. Aflatoxin Bj is metabolized by the enzyme system cytochrome P450 in the liver to a chemically reactive metabolite (see pp. 19-23 and fig. 25), which reacts with molecules such as DNA and protein in liver cells. 

Serious liver disease can affect the 12 main metabolic functions of the liver, with their 60 - 70 even more important partial functions, to widely differing degrees, (s. tab. 3.1) The result is either global insufficiency or partial insufficiency, each with very varied clinical and biochemical symptoms. The failure of certain metabolic functions is responsible to a greater or lesser extent for the development and intensity of liver insufficiency. Impairments in the functions of detoxification and protein metabolism are particularly significant in this respect. 

Numerous proteins are produced in the liver. Genetically induced disorders of protein metabolism may cause pro-... 

Kondrup, J., Nielsen, K., Juul, A. Effect of long-term refeeding on protein metabolism in patients with cirrhosis of the liver. Brit. X. Nutr. 1997 77 197-212... 

The effects of injury and corticoid administration on protein metabolism differ significantly in animals. The content of liver nitrogen is increased by giving cortisone to rats but fracture of the femur does not have this effect in spite of increased levels of cortisol in the blood (M13). The administration of cortisone has a constant effect on nitrogen balance at all levels of nitrogen intake whereas the catabolic response to injury is reduced or even abolished by diminished protein intake and weight loss prior to injury (M12). 

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