Abstract
The aim of this study was to observe the effects of strophanthin induced inhibition of the Na-/K-ATPase in liver cells using a magnetic resonance (MR) compatible bioreactor. A microcavity array with a high density three-dimensional cell culture served as a functional magnetic resonance imaging (MRI) phantom for sodium multi quantum (MQ) spectroscopy. Direct contrast enhanced (DCE) MRI revealed the homogenous distribution of biochemical substances inside the bioreactor. NMR experiments using advanced bioreactors have advantages with respect to having full control over a variety of physiological parameters such as temperature, gas composition and fluid flow. Simultaneous detection of single quantum (SQ) and triple quantum (TQ) MR signals improves accuracy and was achieved by application of a pulse sequence with a time proportional phase increment (TQTPPI). The time course of the Na-/K-ATPase inhibition in the cell culture was demonstrated by the corresponding alterations of sodium TQ/SQ MR signals.
Highlights
Assessment of protein function has long been an overarching goal in biological sciences
Schepkin et al observed an increase in the sodium triple quantum (TQ) signal in an isolated perfused rat heart during sodium-potassium pump (Na-/K-ATPase) blockage induced by strophanthin[12]
We demonstrated for the first time the ability to monitor the changes in sodium activity in a tissue-like 3D-cell culture system using multi quantum (MQ) sodium nuclear magnetic resonance (NMR)
Summary
Assessment of protein function has long been an overarching goal in biological sciences. They found out that the intracellular sodium concentration is sensitive to the presence of lithium[33] Most of these studies record double and triple quantum resonances separate from single quantum resonances using two different pulse sequences. The first results of the in vivo application of the TQTPPI pulse sequence for sodium and potassium was demonstrated by Schepkin et al.[11] In their work they demonstrated the accuracy of the method and presented a model to estimate extra- and intracellular fractions of bound sodium and potassium in a rat head from the ratio of the TQ/SQ signals. Another interesting result was the observation of a competition for binding sites between sodium and potassium in agarose samples. Several aspects of cell suspensions are not in vivo mimetic including perfusion and cell signaling, limiting the scope of previously obtained findings
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