Absence of pH changes during altered work in the in vivo sheep heart: a 31P-NMR investigation.


Saturation transfer from gamma-ATP to inorganic phosphate was used to assign the intracellular inorganic phosphate resonance of the phosphorus-31 nuclear magnetic resonance spectrum of heart obtained from adult sheep under Halothane anesthesia. The 31P chemical shift of intracellular inorganic phosphate was then used as a probe of myocardial pH. Resting myocardial pH was found to be 7.03 +/- 0.02. The effects of increasing myocardial work on myocardial pH were examined using external pacing and phenylephrine infusion alone or in combination to produce steady-state increases in the rate-pressure product. No alteration in myocardial pH was observed with up to 4-fold increases in rate-pressure product. No changes in high-energy phosphates were observed except at the highest rate-pressure products obtained, where small increases in inorganic phosphate and decreases in the phosphocreatine/ATP ratio were observed. In addition, the transition to a new steady state was studied with a 20-s time resolution after initiation of pacing. Again, no changes in pH or levels of phosphates were detected during the transition to increased work.


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@article{Detre1990AbsenceOP, title={Absence of pH changes during altered work in the in vivo sheep heart: a 31P-NMR investigation.}, author={John A. Detre and Alan P. Koretsky and Denise S. Williams and C Kiong Ho}, journal={Journal of molecular and cellular cardiology}, year={1990}, volume={22 5}, pages={543-53} }