Effect of ornithine and lactate on urea synthesis in isolated hepatocytes

1. In hepatocytes isolated from 24 h-starved rats, urea production from ammonia was stimulated by addition of lactate, in both the presence and the absence of ornithine. The relationship of lactate concentration to the rate of urea synthesis was hyperbolic. 2. Other glucose precursors also stimulated urea production to varying degrees, but none more than lactate. Added oleate and butyrate did not stimulate urea synthesis. 3. Citrulline accumulation was largely dependent on ornithine concentration. As ornithine was increased from 0 to 40 mM, the rate of citrulline accumulation increased hyperbolically, and was half-maximal when ornithine was 8-12 mM. 4. The rate of citrulline accumulation was independent of the presence of lactate, but with pyruvate the rate increased. 5. The rate of urea production continued to increase as ornithine was varied from 0 to 40 mM. 6. It was concluded that intermediates provided by both ornithine and lactate are limiting for urea production from ammonia in isolated liver cells. It was suggested that the stimulatory effect of lactate lies in increased availability of cytosolic aspartate for condensation with citrulline.

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Relationship between the resting metabolic rate and hepatic metabolism in rats: effect of hyperthyroidism and fasting for 24 hours

Journal of Endocrinology ◽

10.1677/joe.0.1350045 ◽

1992 ◽

Vol 135 (1) ◽

pp. 45-51 ◽

Cited By ~ 10

Author(s):

S. Iossa ◽

G. Liverini ◽

A. Barletta

Keyword(s):

Oxygen Consumption ◽

Metabolic Rate ◽

Resting Metabolic Rate ◽

Hepatic Metabolism ◽

Isolated Hepatocytes ◽

Liver Cells ◽

Isolated Liver Cells ◽

Rat Liver Cells ◽

The Relationship ◽

Isolated Liver

ABSTRACT We have examined the relationship between the changes in resting metabolic rate (RMR) and those in hepatic metabolism induced by hyperthyroidism and fasting for 24 h. We found that hyperthyroidism induced a significant increase in RMR, while fasting for 24 h reduced RMR in euthyroid but not in hyperthyroid rats. We have also measured oxygen consumption in isolated hepatocytes from euthyroid and hyperthyroid rats, fed or fasted for 24 h. Hyperthyroidism induced an increase in oxygen consumption in rat liver cells; fasting for 24 h increased respiratory rates in isolated liver cells from euthyroid but not from hyperthyroid rats. The findings showed that hyperthyroidism and fasting for 24 h have opposite effects on RMR but similar effects on hepatic metabolism. The results also indicated that the increase in RMR found in hyperthyroid rats is partly due to an increase in hepatic metabolism, while no correlation exists between variations in resting and hepatic metabolism induced by 24-h fasting. Journal of Endocrinology (1992) 135, 45–51

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Parathyroid hormone stimulation of glucose and urea production in isolated liver cells

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1974.227.5.1058 ◽

1974 ◽

Vol 227 (5) ◽

pp. 1058-1061 ◽

Cited By ~ 47

Author(s):

MA Moxley ◽

NH Bell ◽

SR Wagle ◽

DO Allen ◽

J Ashmore

Keyword(s):

Parathyroid Hormone ◽

Liver Cells ◽

Hormone Stimulation ◽

Isolated Liver Cells ◽

Urea Production ◽

Isolated Liver ◽

Stimulation Of

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Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis

Biochemical Journal ◽

10.1042/bj1860035 ◽

1980 ◽

Vol 186 (1) ◽

pp. 35-45 ◽

Cited By ~ 11

Author(s):

A J Dickson ◽

C I Pogson

Keyword(s):

Protein Synthesis ◽

Rat Liver ◽

Isolated Hepatocytes ◽

Liver Cells ◽

Liver Protein ◽

Isolated Cells ◽

Isolated Liver Cells ◽

Rat Liver Cells ◽

Isolated Liver

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

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Metabolic organization of liver during spawning migration of sockeye salmon

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1983.245.6.r827 ◽

1983 ◽

Vol 245 (6) ◽

pp. R827-R830 ◽

Cited By ~ 6

Author(s):

C. J. French ◽

P. W. Hochachka ◽

T. P. Mommsen

Keyword(s):

Amino Acids ◽

Sockeye Salmon ◽

De Novo ◽

Isolated Hepatocytes ◽

Liver Cells ◽

Spawning Migration ◽

Isolated Liver Cells ◽

Metabolic Organization ◽

Gluconeogenesis From Alanine ◽

Isolated Liver

Although earlier studies have established broad outlines of biochemical changes during salmon spawning migration, the metabolic organization of specific organs has hitherto remained unknown. In this study, we assessed the performance of isolated liver cells from anorexic female sockeye salmon (Oncorhynchus nerka) at four sampling sites along their 1,150-km spawning migration. Isolated hepatocytes maintain high rates of gluconeogenesis and CO2 release from amino acids and lactate throughout the migration. Alanine, derived from proteolysis of white muscle, constitutes the single most important source for de novo synthesis of glucose. Just before spawning, when glycogen reserves reach a maximum, gluconeogenesis from alanine is specifically inhibited, whereas its conversion to CO2 and the utilization of other substrates are relatively unchanged. Spawning, apparently supported by carbohydrate catabolism, is accompanied by depletion of glycogen reserves from muscle as well as liver and a stimulation of gluconeogenesis from amino acids. At the onset of migration, palmitate oxidation accounts for about half the CO2 released by liver cells; its contribution decreases during the migration and is negligible after spawning.

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