In Vitro and in Vivo13C and 31P NMR analyses of phosphocholine metabolism in rat glioma cells

✍ Scribed by Robert J. Gillies; Judith A. Barry; Brian D. Ross

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 900 KB
• Volume: 32
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910320306

✦ Synopsis

Abstract

In ivivo magnetic resonance spectroscopy (MRS) has revealed that phsophomonoesters (PME) such as phosphocholine (PCho) and phosphoethanolamine (PEth) are elevated in tumalrs and rapidly proliferating tissues. The regulation of PME levels and their relationship to proliferation are not well known. In the present study, we investigated the regulation of PCho and PEth levels in rat glioma cells grown in vivo and in vitro using ^31^P and ^13^C MRS. However, the ability of cells to produce choline endogenously is variable. To fully understand regulation of PCho levels, it is necessary to characterize the activity of the endogenous pathway, if it exists. This was first investigated by following the metabolic fate of ^13^C‐labeled methionine of 9L glioma tumors in vivo. Our results indicate that there is a significant amount of de novo choline synthesis in ivivo. However, similar experiments performed in virro using cells cultured in bioreactors indicated that glioma cells themselves are unable to synthesize choline de novo, suggesting that the in vivo results were due to the involvement of extra‐tunnoral organs, e.g., liver. Further in vitro experiments demonstrated that the uptake and phosphorylation of physiologically relevant concentrations of exogenous choline is very active in these systems. Thus, it appears that the exogenous pathway for PCho biosynthesis predominates and regulates PCho levels in glioma cells. Our results also demonstrate that PCho levels are lowest, and PEth levels are highest, in non‐proliferating cells. These observations indicate that there is a decrease in the biosynthesis of PCho concomitant with a redulction in culture growth. The source of the increased PEth is, as yet, undefined.