[Phosphorus nuclear magnetic resonance studies of the energetic state and of the intracellular pH of the isolated rat heart in the course of ischemia (author's transl)].

Continuous measurements of high energy phosphate compounds and intracellular pH in perfused, beating rat hearts, were performed by 31P nuclear magnetic resonance (NMR). Hearts were placed in a 15 mm NMR tube and perfused at 28 degrees C by conventional methods with a phosphate-free solution. Phosphorus NMR spectra were recorded at 101,3 MHz in a Brucker WP 250 spectrometer. Global mild ischemia was achieved by reducing the coronary flow to 1/10 of its initial value. Changes in creatine phosphate (CP) and inorganic phosphate (Pi) levels and intracellular pH (pHi) were monitored in the course of a 50 min ischemia and during the post-ischemic phase. When the breakdown of CP was less than 30%, the decrease in pHi was about 0.1-0.2 pH unit; for a greater CP decrease, the fall in pHi was about 1 pH unit.