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Ethanolamine inhibits choline uptake in the isolated hamster heart
Insights
Exogenous ethanolamine inhibits choline uptake in hamster hearts, reducing phosphatidylcholine labeling. This effect is competitive, similar to hemicholinium-3, but does not alter intracellular metabolite levels.
Area of Science:
- Biochemistry
- Cardiovascular Physiology
Background:
- Phosphatidylcholine biosynthesis is crucial for cardiac function.
- Ethanolamine is a precursor in phospholipid metabolism.
- Understanding ethanolamine's impact on cardiac choline metabolism is important.
Purpose of the Study:
- To investigate the effect of exogenous ethanolamine on phosphatidylcholine biosynthesis in isolated hamster hearts.
- To determine if ethanolamine affects choline uptake or intracellular metabolism.
Main Methods:
- Isolated hamster hearts were perfused with radiolabeled choline ([Me-3H]choline).
- Varying concentrations of ethanolamine (0.05-0.5 mM) were added during perfusion.
- Incorporation of label into phosphatidylcholine and CDP-choline pathway metabolites was measured.
- Choline uptake inhibition was compared to hemicholinium-3.
Main Results:
- Ethanolamine decreased phosphatidylcholine labeling by 26-63% at 0.1-0.5 mM.
- Similar reductions were observed in CDP-choline pathway metabolites.
- Ethanolamine inhibited choline uptake competitively, similar to hemicholinium-3.
- Intracellular concentrations of choline, phosphocholine, and CDP-choline remained unchanged.
Conclusions:
- Exogenous ethanolamine does not directly affect the rate of phosphatidylcholine biosynthesis.
- The observed decrease in phosphatidylcholine labeling is due to ethanolamine's inhibition of choline uptake.
- Ethanolamine acts as a competitive inhibitor of choline transport in the heart.
Abstract:
The effect of exogenous ethanolamine on phosphatidylcholine biosynthesis in the isolated hamster heart was investigated. Hamster hearts were perfused with [Me-3H]choline in the presence of 0.05-0.5 mM ethanolamine. Incorporation of label into phosphatidylcholine was decreased 26-63% at 0.1-0.5 mM ethanolamine. Similar decreases in the labelling of the metabolites of the CDP-choline pathway were observed at these ethanolamine concentrations. The observed decrease in phosphatidylcholine labelling at 0.1-0.5 mM ethanolamine was attributed to an inhibition of labelled choline uptake by ethanolamine. The inhibitory role of ethanolamine to choline uptake was examined by comparison to hemicholinium-3. Both compounds inhibited choline uptake in a competitive manner. Intracellular choline, phosphocholine and CDP-choline concentrations were not altered under all experimental conditions. It can be concluded that exogenous ethanolamine has no immediate effect on the rate of phosphatidylcholine biosynthesis in the isolated hamster heart. The reduced labelling of phosphatidylcholine in the presence of ethanolamine is a direct result of the reduction of labelled choline taken up by the heart.