title: 31P NMR studies of cultured human tumor cells. Influence of pH on phospholipid metabolite levels and the detection of cytidine 5'-diphosphate choline.
abstract: 202 MHz 31P NMR (11.7 T) was used to study the effects of culture medium pH on the levels of phosphate metabolites in three human tumor cell lines (XP29MAmal, a malignant xeroderma pigmentosum; CX-1, a colon carcinoma; KB, a squamous cell carcinoma of the oral cavity). Cells were cultured in Roux flasks in HAM's F-12 medium, and the pH was varied with the final medium change. After harvesting, 1-5 x 10(8) cells were suspended in Ringer/HEPES buffer at pH 7.4 and 4 degrees C for 31P NMR studies. Cell adhesion and growth rate decreased with decreasing pH, but, down to ca pH 6.1, trypan blue exclusion and the observed levels of nucleoside di- and triphosphates (range: 22-37% of total phosphates detected), phosphocreatine (PCr, 2-5%) and Pi (5-11%) did not vary significantly with pH. For XP29MAmal cells in exponential growth phosphocholine levels decreased from 18-28% at pH 7.0 to ca 5% at pH 6.0, while phosphoethanolamine levels increased from 2-7% to 15%. Glycerophosphocholine (GPC) levels increased from ca 7% at pH 7.2 to 13% at pH 6.3. At pH less than 6.3 cytidine 5'-diphosphate (CDP) choline became detectable (8-16%, delta p:P alpha = -8.13 ppm, P beta = 8.93 ppm, for PCr = 0 ppm). However, confluent cells did not accumulate CDP-choline when the pH was lowered. The cell lines CX-1 and KB also showed the pH effects described herein.
authors.affiliation: Central Spectroscopy Department, German Cancer Research Center, Heidelberg.
authors.forename: A C
authors.initials: AC
authors.lastname: Kuesel
authors.forename: G
authors.initials: G
authors.lastname: Graschew
authors.forename: W E
authors.initials: WE
authors.lastname: Hull
authors.forename: W
authors.initials: W
authors.lastname: Lorenz
authors.forename: H W
authors.initials: HW
authors.lastname: Thielmann
mesh_terms: D002794:Choline / Q000031:analogs & derivatives*; D003470:Culture Media; D003566:Cytidine Diphosphate Choline / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D010743:Phospholipids / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000378:metabolism*
chemical_list: D003470:Culture Media; D010743:Phospholipids; D003566:Cytidine Diphosphate Choline; D002794:Choline