scholarly journals Mechanisms of caeruloplasmin biosynthesis in normal and copper-deficient rats

1992 ◽  
Vol 282 (3) ◽  
pp. 835-839 ◽  
Author(s):  
J D Gitlin ◽  
J J Schroeder ◽  
L M Lee-Ambrose ◽  
R J Cousins
Keyword(s):  
Oxidase Activity ◽  
Copper Deficiency ◽  
Interleukin 1 ◽  
Rat Hepatocytes ◽  
Complete Loss ◽  
Primary Hepatocytes ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Mrna Content ◽  
Rate Limiting

To examine the mechanisms of holo-caeruloplasmin biosynthesis, we measured the serum caeruloplasmin concentration and oxidase activity, hepatic caeruloplasmin mRNA content and hepatocyte caeruloplasmin biosynthesis and secretion in normal and copper-deficient rats. Copper deficiency resulted in a near-complete loss of serum caeruloplasmin oxidase activity, yet only a 60% reduction in serum caeruloplasmin concentration and no change in the abundance of hepatic caeruloplasmin mRNA or the rate of caeruloplasmin biosynthesis. Both interleukin-1 alpha and lipopolysaccharide increased hepatic caeruloplasmin mRNA content and caeruloplasmin biosynthesis in normal and copper-deficient animals, but neither mediator increased caeruloplasmin oxidase activity in the copper-deficient group. Pulse-chase studies in primary hepatocytes from normal and copper-deficient rats revealed that the secretory rates for newly synthesized caeruloplasmin were identical, despite little or no holo-caeruloplasmin synthesis in hepatocytes of copper-deficient rats. We conclude that hepatocyte copper content has no effect on hepatic caeruloplasmin-gene expression or caeruloplasmin biosynthesis and that the incorporation of copper into newly synthesized caeruloplasmin is not a rate-limiting step in the biosynthesis or secretion of the apoprotein from rat hepatocytes.

scholarly journals Biosynthesis, assembly and secretion of fibrinogen in cultured rat hepatocytes

1988 ◽  
Vol 251 (2) ◽  
pp. 373-377 ◽  
Author(s):  
S Hirose ◽  
K Oda ◽  
Y Ikehara
Keyword(s):  
Rat Hepatocytes ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Gamma Subunit ◽  
Intracellular Pool ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Gamma Subunits ◽  
Cultured Rat Hepatocytes ◽  
Rate Limiting

The biosynthesis, assembly and secretion of fibrinogen were investigated in cultured rat hepatocytes which were incubated with [35S]methionine. When initial rates of the synthesis of three fibrinogen subunits were compared, the A alpha-subunit was found to be synthesized significantly slower than the B beta- and gamma-subunits. Pulse-chase experiments revealed that the secreted fibrinogen contained different proportions of the newly synthesized subunits, depending upon the chase times. Radioactivity in the A alpha subunit, which initially had the highest level of the three, was rapidly decreased in parallel with the chase time. The gamma-subunit had an increasing amount of the radioactivity in the secreted molecule during the chase periods, whereas that in the B beta-subunit was gradually decreased at the later stages of chase. Analysis of intracellular components of fibrinogen confirmed that the nascent A alpha-subunit was most rapidly exhausted, and the gamma-subunit occupied the largest proportion among the non-assembled subunits at later stages of chase. Taken together, these results suggest that the synthesis of A alpha-subunit, which has the lowest rate, could be the rate-limiting step in the production and secretion of fibrinogen in cultured rat hepatocytes, in contrast with what has been proposed for human and rabbit fibrinogen, namely that the synthesis of B beta-subunit is the rate-limiting step. The results also indicate that there is a large intracellular pool of gamma-subunit.

Hypoxia inhibits the induction of argininosuccinate synthetase by endotoxin in lung endothelial cells

1997 ◽  
Vol 272 (5) ◽  
pp. L934-L938 ◽  
Author(s):  
Y. Su ◽  
E. R. Block
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cells ◽  
Actinomycin D ◽  
Nitric Oxide Production ◽  
Argininosuccinate Synthetase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Mrna Content ◽  
Lung Endothelial Cells ◽  
Rate Limiting

Pulmonary artery endothelial cells (PAEC) possess a two-step pathway for synthesizing L-arginine from L-citrulline. The first and rate-limiting step is catalyzed by argininosuccinate synthetase (AS). We have previously shown that hypoxia inhibits synthesis of L-arginine from L-citrulline in PAEC. In this study, we examined the effect of hypoxia on the induction of AS in PAEC. Porcine PAEC were incubated with or without endotoxin under normoxia (air-5% CO2) or hypoxia (0% O2-95% N2-5% CO2) for 24 h, and then AS activity and AS mRNA content were determined. Incubation with endotoxin resulted in increases in AS activity and mRNA, and the latter was blocked by actinomycin D. Exposure to hypoxia for 24 h decreased AS activity and mRNA content and stability, and it also abolished the increases in AS activity and mRNA induced by endotoxin. These results indicate that hypoxia inhibits endotoxin-mediated induction of AS. This inhibition might reduce the availability of intracellular L-arginine and thereby limit immunostimulant-induced nitric oxide production by lung endothelial cells.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

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