title: 31P nuclear magnetic resonance measurements of intracellular pH in giant barnacle muscle.
abstract: The accuracy of intracellular pH (pHi) measurements by 31P nuclear magnetic resonance (NMR) spectroscopy was examined in single muscle fibers from the giant barnacle, Balanus nubilis. The pHi was derived from the chemical shifts of 2-deoxy-D-glucose-6-phosphate and inorganic phosphate. In fibers superfused with sea water at pH 7.7, pHi = 7.30 +/- 0.02 at 20 degrees C. Experimentally induced pHi changes were followed with a time resolution of 3 min. Intracellular alkalinization was induced by exposure to NH4Cl and intracellular acidification followed when NH3 was removed. Then acid extrusion was stimulated by exposure to bicarbonate containing sea water. In single muscle fibers 31P NMR results were in excellent agreement with microelectrode studies over the pH range of 6.5 to 8.0. The initial acid extrusion rate was 1.7 +/- 0.3 mmol X l-1 X min-1 at pHi 6.75. Our results showed that 31P NMR is a reliable in vivo pH probe.
mesh_terms: D000818:Animals; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives*; D005958:Glucosephosphates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009132:Muscles / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism; D001468:Thoracica
chemical_list: D005958:Glucosephosphates; D010710:Phosphates; C015785:2-deoxyglucose-6-phosphate; D019298:Glucose-6-Phosphate; D008274:Magnesium