Choline glycerophospholipid biosynthesis in the guinea pig heart

1987 ◽  
Vol 65 (10) ◽  
pp. 860-868 ◽  
Author(s):  
Monika Wientzek ◽  
Ricky Y. K. Man ◽  
Patrick C. Choy
Keyword(s):  
Guinea Pig ◽  
Choline Kinase ◽  
Major Pathway ◽  
Guinea Pig Heart ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Choline Glycerophospholipids ◽  
Mammalian Liver ◽  
Rate Limiting

The aims of this study were to (i) elucidate the biosynthetic pathways for the formation of plasmenylcholine in the mammalian heart and (ii) investigate whether the control of choline glycerophospholipid production is different in hearts with high plasmenylcholine content. Guinea pig hearts were used throughout this study, since 34% of the cardiac choline glycerophospholipids in this species is present in the plasmenylcholine form. By perfusion of the guinea pig heart in the Langendorff mode with labeled choline, we demonstrated that the majority of plasmenylcholine in the heart was synthesized via the CDP-choline pathway. The ability of the heart to form plasmenylcholine from CDP-choline and 1-alkenyl-2-acylglycerol was also shown. We postulate that 1-alkenyl-2-acylglycerol in the guinea pig heart might originate from the hydrolysis of plasmenylethanolamine. In mammalian liver and other tissues, the CDP-choline pathway is the major pathway for phosphatidylcholine biosynthesis and the rate-limiting step is catalyzed by CTP:phosphocholine cytidylyltransferase. The results obtained from the present study support this supposition. In addition, evidence was obtained indicating that phosphorylation of choline by choline kinase in the CDP-choline pathway may also be rate limiting. Although the involvement of choline kinase as a rate-limiting enzyme in the CDP-choline pathway has been shown in a number of cell cultures, the rate-limiting role of this enzyme in intact mammalian organs has not been previously reported. The rationale for the presence of more than one rate-limiting step in the CDP-choline pathway in the guinea pig heart remains undefined.

Effect of cAMP on choline uptake and phosphatidylcholine biosynthesis in cultured chick heart cells

1988 ◽  
Vol 66 (3) ◽  
pp. 231-237 ◽  
Author(s):  
Paul S. Sunga ◽  
P. Haydn Pritchard ◽  
Simon W. Rabkin
Keyword(s):  
Phosphodiesterase Inhibitor ◽  
Cardiac Cells ◽  
Heart Cells ◽  
Choline Uptake ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Phosphatidylcholine Biosynthesis ◽  
Chick Heart ◽  
Rate Limiting

The effect of an analogue of cAMP on the uptake and metabolism of choline in the heart was studied in isolated cardiac cells. The cells were obtained from 7-day-old chick embryos and maintained in culture. The effects of cAMP were studied using the dibutyryl cAMP analogue and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. After a 2-h incubation with [3H]choline, about 85% of the label was recovered in phosphocholine, with most of the rest in phospholipid. During a subsequent chase incubation, [3H]phosphocholine was transferred to phosphatidylcholine with little accumulation in CDP-choline. This suggests the rate-limiting step for the conversion of phosphocholine to phosphatidylcholine in these cells is the synthesis of CDP-choline. cAMP decreased the incorporation of choline into phosphatidylcholine, but did not change the flux of metabolites through the step catalyzed by CTP:phosphocholine cytidylyltransferase. cAMP had little effect on choline uptake at low (1–25 μM) extracellular choline concentrations, but significantly (p < 0.05) decreased choline uptake at higher (37.5–50 μM) extracellular choline concentrations. Thus, cardiac cells take up and metabolize choline to phosphocholine, with CTP:phosphocholine cytidylyltransferase being the rate-limiting step in phosphatidylcholine biosynthesis. cAMP decreases [3H]choline uptake and its subsequent incorporation into phosphocholine and phospholipid. However, the metabolism of choline within the cell is unaffected.

Regulation of phosphatidylcholine metabolism in mammalian hearts

1989 ◽  
Vol 67 (2-3) ◽  
pp. 67-77 ◽  
Author(s):  
Grant M. Hatch ◽  
Karmin O ◽  
Patrick C. Choy
Keyword(s):  
Phospholipase A ◽  
Current Evidence ◽  
Major Phospholipid ◽  
Mammalian Heart ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Phosphatidylcholine Biosynthesis ◽  
Rate Limiting ◽  
Phosphatidylcholine Metabolism

Phosphatidylcholine is the major phospholipid in the mammalian heart. Over 90% of the cardiac phosphatidylcholine is synthesized via the CDP-choline pathway. The rate-limiting step of this pathway is catalyzed by CTP:phosphocholine cytidylyltransferase. Current evidence suggests that phosphatidylcholine biosynthesis in the heart is regulated by the availability of CTP and the modulation of cytidylyltransferase activity. Phosphatidylcholine is degraded mainly by the actions of phospholipase A1 and A2, with the formation of lysophosphatidylcholine. Lysophosphatidylcholine may be further deacylated by lysophospholipase or reacylated back into the parent phospholipid by the action of acyltransferase. The accumulation of lysophosphatidylcholine in the heart may be one of the biochemical factors for the production of cardiac arrhythmias.Key words: phosphatidylcholine, phospholipids, biosynthesis, metabolism, heart.

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
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