title: Effect of cAMP on choline uptake and phosphatidylcholine biosynthesis in cultured chick heart cells.
abstract: 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 microM) extracellular choline concentrations, but significantly (p less than 0.05) decreased choline uptake at higher (37.5-50 microM) 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.
authors.affiliation: Department of Medicine, University of British Columbia, Shaughnessy Hospital Lipid Research Group, Vancouver, Canada.
authors.forename: P S
authors.initials: PS
authors.lastname: Sunga
authors.forename: P H
authors.initials: PH
authors.lastname: Pritchard
authors.forename: S W
authors.initials: SW
authors.lastname: Rabkin
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D002794:Choline / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000096:biosynthesis*
chemical_list: D010713:Phosphatidylcholines; D000242:Cyclic AMP; D002794:Choline