Incorporation Rate in Vitro of Choline and Methyl-Methionine into Human Hepatic Lecithins

Abstract

Lindblad, L. & Scherstén, T. Incorporation rate in vitro of choline and methyl-methionine into human hepatic lecithins. Scand. J. Gastroent. 1976, 11, 587-591

In order to evaluate the quantitative role of cytidinediphosphate-choline and phosphatidyl-ethanolamine-methylation pathways in the synthesis of phosphatidylcholine in human liver tissue, the incorporation rate of [¹⁴C]choline and [¹⁴C]methyl-methionine into liver lecithins was determined. Liver biopsy was taken in 27 patients operated upon for uncomplicated gallstone disease. Linear incorporation into lecithin was achieved for N-methyl-methionine during 4 hours’ incubation and for choline from 7.5 min to 60 min of incubation but with a significant positive Y-interccpt. This Y-intercept was directly proportional to the concentration of choline in the medium and might be explained by a rapid base exchange between free choline in the medium and bases in phosphoglycerides. Fertile women showed significantly higher incorporation rate of methyl-methionine than postmenopausal women. Bile acids in the incubation medium did not influence the incorporation rate of these precursors into hepatic lecithin: The results indicate that the contribution of the méthylation pathway in the synthesis of human liver lecithin accounts for about 10-15 per cent of that of the CDP-choline pathway.

Key-words::

• Base exchange
• bile acids
• cytidinediphosphate-choline pathway
• lecithin synthesis, human liver
• methylation pathway