Intracellular pH of frog sartorius muscle
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Summary
Morpholine, a weak base, is suitable for measuring intracellular pH in frog muscle. However, different pH measurement methods yielded conflicting results, suggesting unique intracellular water properties.
Area of Science:
- Physiology
- Biophysics
Background:
- Intracellular pH (pH(i)) is a critical physiological parameter.
- Accurate measurement of pH(i) is essential for understanding cellular function.
- Weak bases like morpholine can serve as pH indicators.
Purpose of the Study:
- To evaluate morpholine as an indicator for intracellular pH measurement.
- To compare pH(i) values obtained using morpholine with other methods.
Main Methods:
- Radiolabeled morpholine (³H-morpholine) distribution in frog sartorius muscle.
- Determination of morpholine's pK'a in a solution mimicking frog Ringer.
- Comparison of pH(i) measurements using morpholine, nicotine, 5,5'-dimethyl-2,4-oxazolidinedione, and pH-sensitive microelectrodes.
Main Results:
- Morpholine's pK'a (8.45 ± 0.02 at 20°C) is within the optimal range for pH sensitivity.
- Morpholine demonstrated no binding, metabolism, or toxicity in the studied concentrations.
- Significant discrepancies were observed between pH(i) values obtained from different measurement techniques.
Conclusions:
- Morpholine is a suitable indicator for intracellular pH determination.
- Discrepant pH(i) values suggest potential differences in water structure and solvent properties between intracellular and extracellular compartments.
- Intracellular pH may be higher than previously estimated, and its precise determination is complex.