Intracellular pH determination by 13C-NMR spectroscopy

Area of Science:

• Biochemistry
• Physiology
• Medical Imaging

Background:

• Accurate intracellular pH (pHi) measurement is crucial for understanding cellular function and disease.
• Existing methods for pHi determination can be invasive or lack precision in specific physiological ranges.

Purpose of the Study:

• To develop and validate a novel noninvasive method for determining intracellular pH using 13C-NMR spectroscopy.
• To assess the utility of this method in quantifying pHi in intact tissues, particularly under ischemic conditions.

Main Methods:

• Utilized the 13C-nuclear magnetic resonance (NMR) chemical shift of the C-3 carbon of sn-glycerol 3-phosphate as a pH indicator.
• Employed nonlinear least-squares analysis to determine the pKa of sn-glycerol 3-phosphate at 37°C.
• Correlated 13C-NMR pHi measurements with simultaneous 31P-NMR spectroscopy in intact rat hearts during normal and ischemic perfusion.

Main Results:

• The C-3 resonance of sn-glycerol 3-phosphate exhibited a pKa of 6.2, indicating sensitive pH detection in the range of approximately 5-7.
• 13C-NMR determined intracellular pH values showed strong correlation with 31P-NMR measurements across a broad pH range.
• The method demonstrated reliability in intact rat hearts under both normal and ischemic physiological conditions.

Conclusions:

• The described 13C-NMR method provides a sensitive and noninvasive approach for quantifying intracellular pH in intact tissues.
• This technique is particularly well-suited for monitoring physiological pH changes in conditions such as myocardial ischemia.
• The findings support the application of this NMR-based method for in vivo pH assessment in biomedical research.