3-aminopropylphosphonate (3-APP) is known for its use as an exogenous indicator of extracellular volume and pH in phosphorus-31 nuclear magnetic resonance (31P NMR) studies. We used 3-APP for estimating the extracellular volume in NMR studies of several ex vivo preparations including retrograde perfused mouse heart (n = 4), mouse liver slices (n = 2), xenograft breast cancer tumors (n = 7, MCF7), and rat brain slices (n = 4). In the former three preparations, the 3-APP signal was stable in lineshape and intensity for hours and the chemical shift of the signal in the presence of the biological sample was the same as in the perfusion medium without the biological sample. However, in studies of brain slices, the 3-APP signal appeared split into two, with an upfield component (0.7 ± 0.1 ppm to the left) increasing with time and showing a wider linewidth (66.7 ± 12.6 vs. 39.1 ± 7.6 Hz, the latter is of the perfusion medium signal). This finding suggests that 3-APP inadvertently accumulated in brain slices, most likely as a membrane bound form. This observation limits the use of 3-APP as an inert biochemical indicator in brain preparations and should be taken into account when using 3-APP in vivo.
Bibliographical noteFunding Information:
Israel Science Foundation; Grant Agreement Number: 1379/18. Funding information
The authors wish to thank Drs. Talia Harris, Atara Nardi‐Schrieber, Gal Sapir, Yael Adler‐Levi, Ayelet Gamliel, and Sivaranjan Uppala, and Mr. Assad Azar for assistance with data collection in the initial phase of this project. This study was funded by the Israel Science Foundation under grant agreement no. 1379/18, by the European Commission (Grant/Award Number: 858149 – AlternativesToGd), and the Jabotinsky Scholarship of the Israeli Ministry of Science and Technology for Applied and Engineering Sciences for Direct PhD Students (No. 3‐15892 for DS).
© 2022 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.
- 3-APA 3-aminopropanephosphinic acid
- 3-APP 3-aminopropylphosphonate
- 31P phosphorous NMR spectroscopy
- ATP adenosine triphosphate