Phosphorous metabolites and steady-state energetics of transformed fibroblasts during three-dimensional growth.
Rat1-T1 and MR1 spheroids represent separate transformed phenotypes originated from the same rat fibroblasts that differ in three-dimensional (3D) growth kinetics, histological structure, and oxygenation status. In the present study, (31)P-NMR spectroscopy of perfused spheroid suspensions was used to investigate cellular energetics relative to 3D growth, development of necrosis, and cell cycle distribution. Both spheroid types were characterized by a remarkably low amount of free (inorganic) phosphate (P(i)) and a low phosphocreatine peak. The ratio of nucleoside triphosphate (NTP) to P(i) ranged between 1.5 and 2.0. Intracellular pH, NTP-to-P(i) ratio, and NTP/cell remained constant throughout spheroid growth, being unaffected by the emergence of oxygen deficiency, cell quiescence, and necrosis. However, a 50% decrease in the ratio of the lipid precursors phosphorylcholine and phosphorylethanolamine (PC/PE) was observed with increasing spheroid size and was correlated with an increased G(1)/G(0) phase cell fraction. In addition, the ratio of the phospholipid degradation products glycerophosphorylcholine and glycerophosphorylethanolamine (GPC/GPE) increased with spheroid diameter in Rat1-T1 aggregates. We conclude that changes in phospholipid metabolism, rather than alterations in energy-rich phosphates, reflect cell quiescence in spheroid cultures, because cells in the inner oxygen-deficient zones seem to adapt their energy metabolism to the environmental conditions before necrotic cell destruction.
Kunz-Schughart
Leoni A
LA
Langham Resource, Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Freyer
James P
JP
D000818:Animals; D002455:Cell Division / Q000502:physiology; D002461:Cell Line, Transformed; D015194:Diffusion Chambers, Culture / Q000295:instrumentation; D004734:Energy Metabolism; D004983:Ethanolamines / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D016193:G1 Phase / Q000502:physiology; D005997:Glycerylphosphorylcholine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009336:Necrosis; D010710:Phosphates / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D010759:Phosphorus Isotopes; D010767:Phosphorylcholine / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D016192:Resting Phase, Cell Cycle / Q000502:physiology; D018874:Spheroids, Cellular / Q000166:cytology / Q000378:metabolism*
D004983:Ethanolamines; D010710:Phosphates; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D010759:Phosphorus Isotopes; D010725:Phosphocreatine; D010767:Phosphorylcholine; C002449:glycerophosphoethanolamine; D005997:Glycerylphosphorylcholine; C005448:phosphorylethanolamine