Development of a system for simultaneous 31P NMR and optical transmembrane potential measurement in rabbit hearts

The aim of this study is to develop a system for the first simultaneous measurements using 31P NMR and optical transmembrane potential-sensitive fluorescence. 31P NMR is used to evaluate 5 metabolic markers (pH, sugar phosphates, phosphocreatine, phospholipid intermediates and ATP). Action potential duration is measured with a transmembrane potential-sensitive fluorescent dye, di-4ANEPPS. The system is intended to correlate the action potentials with the metabolic markers and their changes during the time course of cardiac ischemia. The requirements of this system include fabrication of a NMR probe large enough for rabbit heart experiments, incorporation of light guides for excitation of dye and collection of fluorescence in hearts located within a NMR magnet and with minimal disturbance of the magnetic field. The quality factor (Q) of the probe's coil was measured. Control NMR spectra were then acquired with phosphorus test solution. Further spectra were obtained after addition of the optical elements. Results show the ability to use our new probe to acquire a spectrum in the presence of the optical elements within the magnet, suggesting the possibility that 31P NMR spectroscopy and optical transmembrane potential measurements can be performed simultaneously in hearts.