AJP - Cell Physiology, Vol 252, Issue 1 C30-C37, Copyright © 1987 by American Physiological Society
31P nuclear magnetic resonance measurements of intracellular pH in giant barnacle muscle
J. R. Hamm and G. M. Yue
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.
