In Vitro Monitoring of Total Choline Levels in a Bioartificial Pancreas: 1H NMR Spectroscopic Studies of the Effects of Oxygen Level

Robert C. Long, Klearchos K Papas, Athanassios Sambanis, Ioannis Constantinidis

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Abstract

This investigation implements specifically designed solvent-suppressed adiabatic pulses whose properties make possible the long-term monitoring of 1H NMR detectable metabolites from alginate/poly-L-lysine/alginate (APA)-encapsulated βTC3 cells. Our encapsulated preparations were maintained in a perfusion bioreactor for periods exceeding 30 days. During this prolonged cultivation period, the cells were exposed to repetitive hypoxic episodes of 4 and 24 h. The ratio of the total choline signal (3.20 ppm) to the reference signal (observed at 0.94 ppm assigned to isoleucine, leucine, and valine) decreased by 8-10% for the 4-h and by 20-32% for the 24-h episodes and returned to its prehypoxic level upon reoxygenation. The decrease in the mean value of total choline to reference signal ratio for three 4-h and two 24-h episodes in two different cultures was highly significant (P < 0.01). The rate of recovery by this ratio was slower than the rates of recovery by oxygen consumption, lactate production, or glucose consumption. A step-up in oxygen level led to a new, higher value for the total choline to reference ratio. From spectra of extracts at 400 MHz, it was determined that 63.6% of the total choline signal is due to intracellular phosphorylcholine. Therefore, it is inferred that the observed changes in total choline signal are linked to an oxygen level dependence of the intracellular phosphorylcholine. Several possible mechanisms in which oxygen may influence phosphorylcholine metabolism are suggested. In addition, the implications of these findings to the development of a noninvasive monitoring method for tissue-engineered constructs composed of encapsulated cells are discussed.

Original languageEnglish (US)
Pages (from-to)49-57
Number of pages9
JournalJournal of Magnetic Resonance
Volume146
Issue number1
DOIs
Publication statusPublished - Sep 2000
Externally publishedYes

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Keywords

  • βTC3 insulinoma cells
  • H NMR
  • Hypoxia
  • Total choline

ASJC Scopus subject areas

  • Molecular Biology
  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Radiology Nuclear Medicine and imaging
  • Condensed Matter Physics

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