Increase of GPC levels in cultured mammalian cells during acidosis. A 31P MR spectroscopy study using a continuous bioreactor system

Abstract

The purpose of this study was to study the metabolic events during a slow acidosis in three different cell lines by combining 31P magnetic resonance spectroscopy and hollow fiber bioreactor technology. The rate of change in intracellular pH, glycerophosphorylcholine (GPC), phophorylcholine (PCho), and nucleoside-triphosphate (NTP) levels were measured during 8 h of acidosis and 16 h of recovery in EPO, EAT, and RN1a cells, three cultured mammalians cell lines. Our results show a significant increase in GPC levels to 330 +/- 21.540 +/- 25, and 220 +/- 21% of their initial value correlated to a decrease of PCho levels to 57 +/- 14.58 +/- 17 and 45 +/- 15% of their initial value in EAT, RN1a, and EPO cells, respectively. These changes are discussed in terms of perturbation of energetic metabolism in cells undergoing a slow acidosis.

FIG. 1.

³¹P MRS spectra of (a) EAT, (b) RN1a, and (c) EPO cells at low and high pH. Peak assignments are as follows: (1) Phosphorylethanolomine, (2) glycerophosphorylethanolamine, (3) γ NTP, (4) α NTP, (5) diphosphodiester, (6) UDP-Hexoses, (7) β NTP.

FIG. 2.

Changes in pH and relative concentrations of GPC, PCho, and NTP in EAT, RN1a, and EPO perfused cells during 8 h of acidosis followed by 16 h of recovery.

FIG. 3.

Pathways of synthesis and catabolism of phosphatidylcholine. Our results suggest that in the three cell lines the degradation of PCho is due to the action of a phospholipase type 2, leading to the formation of GPC, rather than phospholipase C or D (these enzymatic reactions do not yield GPC, and they would not affect the levels of PCho).