Effect of Albumin Concentration and Colloid Osmotic Pressure on Albumin Synthesis in the Perfused Rat Liver

Dich, John; Hansen, Svend E.; Thieden, H. I. D.

doi:10.1111/j.1748-1716.1973.tb05530.x

Cited by 42 publications

(11 citation statements)

References 19 publications

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“…In the present study the basal rate of albumin secretion was 4.6 pglmin per g liver wet wt. This is in agreement with observations in the perfused liver (Hoffenberg, Gordon andBlack 1971, Dich, Hansen andThieden 1973) and is about 40% of the in vivo rate (Peters and Peters 1972). Compared with our previous study (Dich and Gluud 1975) a 3-fold increase in the rate of albumin secretion has been obtained; also the incorporation of leucine into albumin and total proteins in the medium and in the cell suspension was increased.…”

Section: Protein Metabolismsupporting

confidence: 92%

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of ¹⁴C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Dich

Gluud

1976

Acta Physiologica Scandinavica

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Parenchymal rat liver cells were isolated by the collagenase method and incubated in Krebs-Henseleit buffer containing 0.5% gelatin. The basal level of cyclic AMP in isolated cells was 0.52 nmol per g liver wet wt. Glucagon (10(-10)-10(-6) M) caused a significant increase in the level of cyclic AMP. Maximum levels were obtained 2-15 min after addition of glucagon. Repeated administration of glucagon caused a new increase in cyclic AMP, but the response was lesser than after the first addition of glucagon, indicating refractoriness to glucagon. The rate of albumin secretion was 4.6 mug/min per g liver wet wt. This is about the rate found in the perfused liver, Glucagon (10(-8-10(-6) M) inhibited albumin secretion and the incorporation of 14C-leucine into albumin, into total proteins in the medium and into total proteins in the cell suspension. The effect of glucagon on albumin secretion is compatible with an effect on the rate of synthesis. A positive correlation existed between the maximal level of cyclic AMP after glucagon administration and the inhibition of both albumin secretion and the incorporation of 149leucine.

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Section: Protein Metabolismsupporting

confidence: 92%

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of ¹⁴C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Dich

Gluud

1976

Acta Physiologica Scandinavica

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“…The interplay of these vasoactive peptides on a systemic basis may, therefore, influence the metabolic function of specific organs, as recently suggested for volume regulatory responses modulating hepatic ammonia metabolism (44). However, since an inhibitory effect on albumin synthesis by colloids has also been described in ex vivo systems (16)(17)(18) (47)(48)(49). Studies are now in progress to identify specific 5' upstream sequences in the albumin gene that confer the regulatory response to this novel feedback regulatory mechanism.…”

Section: Discussionmentioning

confidence: 99%

“…Other studies extended this observation to macromolecules other than albumin, and it was proposed that all these agents may work through a common feedback mechanism based on their ability to influence the COP (17,18). However, the molecular basis for this regulation has never been identified, and at present it is not known whether the proposed feedback regulation operates on albumin synthesis at the transcriptional, posttranscriptional, or translational level or on albumin secretion.…”

Section: Introductionmentioning

confidence: 99%

Albumin gene expression is down-regulated by albumin or macromolecule infusion in the rat.

Pietrangelo¹,

Panduro²,

Chowdhury³

et al. 1992

J. Clin. Invest.

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IntroductionA novel feedback regulatory mechanism operating on transcription of the albumin gene is described in the rat. In 1946, it was proposed that circulating colloids, including serum albumin, may affect the synthesis and/or secretion ofalbumin in the liver. The molecular basis for this proposed regulation has now been investigated by adding oncotically active macromolecules to the circulation of normal or genetically albumin-deficient Nagase analbuminemic rats (NAR) and analyzing the hepatic expression of genes, including albumin after 24 h. The transcription rate of the albumin gene was higher in NAR than in normal rats and was dramatically reduced by raising serum albumin to 1.6 g/dl. Intravenous infusion of albumin into normal rats also decreased transcriptional activity of the albumin gene by 50-60%, and this decrease correlated with changes in serum colloid osmotic pressure after albumin infusion. Inhibition ofalbumin gene transcription was also observed upon intravenous infusion of other protein or nonprotein macromolecules, such as y-globulin and dextran. This down-regulation appears to control the steady-state level of albumin mRNA in the liver.Aside from a concomitant decrease in apo E gene transcription after albumin or macromolecule infusion, there was no change in the transcription rate of other genes, including those exhibiting liver-preferred or -specific expression (e.g., tyrosine aminotransferase, cytochrome P450, a1-antitrypsin, apolipoproteins A-I and B, and transferrin) or general cellular expression (e.g., a-tubulin, pro a2 collagen, and fl-actin). The liver represents the main source of serum albumin (1, 2). Normally, the plasma albumin concentration remains constant at 3.5-4.0 g/dl, suggesting an active regulation ofalbumin metabolism. Several pathophysiological studies have shown that hormones, malnutrition, and stress may influence albumin synthesis (3-7); however, little is known about the "physiological" regulator(s) of albumin or other proteins synthesized by the liver. Many years ago, Biorneboe (8, 9) observed that an increase in the serum concentration ofglobulins is followed by a concomitant decrease ofserum albumin in hepatitis and after immunization, and he proposed that the serum colloid osmotic pressure (COP)' might serve as a regulator for changes in serum protein concentration. In support ofthis hypothesis, hyperglobulinemia, infusion of y-globulin, and administration of dextran were also shown to decrease serum albumin levels (10-12). Moreover, in a variety ofconditions in which serum albumin levels fall either acutely (e.g., plasmapheresis) or chronically (e.g., nephrotic syndrome), hepatic albumin synthesis is increased (13)(14)(15).In the 1960's, Rothschild et al. (16) demonstrated that addition of albumin to the perfusate medium ofthe isolated rabbit liver decreases incorporation of labeled amino acids into albumin. Other studies extended this observation to macromolecules other than albumin, and it was proposed that all these agents may work through a com...

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“…Conditions that cause an increase in plasma rc reduce the rate of albumin synthesis in vivo [31][32][33][34][35]. Although the rate of albumin synthesis responds to changes in r~ in isolated perfused organs [35], there is no clear relationship between serum albumin concentration and the rate of albumin synthesis in nephrotic patients [3,4,30] or animals [11]. While the rate of albumin synthesis increases in direct proportion to albuminuria in both nephrotic patients [4,30] and animals [11], this response nevertheless fails to maintain albumin pools or serum concentration in or near the normal range.…”

Section: Discussionmentioning

confidence: 99%

Ineffectiveness of dietary protein augmentation in the management of the nephrotic syndrome

Al-Bander

Kaysen

1991

Pediatr Nephrol

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The nephrotic syndrome is a consequence of altered permselectivity of the glomerular basement membrane resulting in urinary losses of albumin and other serum proteins. Although dietary protein augmentation increases albumin synthesis, it has not been shown to increase serum albumin or muscle protein. Dietary protein was increased from 8.5% to 21% in pair-fed rats with Heymann nephritis and resulted in an increase both in albumin synthesis and urinary albumin excretion, but not in serum albumin concentration or in total albumin pools. The increase in dietary protein was 8 times greater than the resulting increase in urinary protein excretion, but nearly all of the additional ingested protein was catabolized to urea and excreted in the urine rather than used to augment growth. Dietary supplementation with protein has no obvious beneficial effect on nutritional status of nephrotic rats.

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Effect of Albumin Concentration and Colloid Osmotic Pressure on Albumin Synthesis in the Perfused Rat Liver

Cited by 42 publications

References 19 publications

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of ¹⁴C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of ¹⁴C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Albumin gene expression is down-regulated by albumin or macromolecule infusion in the rat.

Ineffectiveness of dietary protein augmentation in the management of the nephrotic syndrome

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Effect of Albumin Concentration and Colloid Osmotic Pressure on Albumin Synthesis in the Perfused Rat Liver

Cited by 42 publications

References 19 publications

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of 14C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of 14C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Albumin gene expression is down-regulated by albumin or macromolecule infusion in the rat.

Ineffectiveness of dietary protein augmentation in the management of the nephrotic syndrome

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Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of ¹⁴C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells

Effect of Glucagon on Cyclic AMP, Albumin Metabolism and Incorporation of ¹⁴C‐Leucine into Proteins in Isolated Parenchymal Rat Liver Cells