AJP - Renal Physiology, Vol 245, Issue 6 792-F800, Copyright © 1983 by American Physiological Society
Response of 31P-nuclear magnetic resonance spectra of frog skin to variations in PCO2 and hypoxia
R. L. Nunnally, J. S. Stoddard, S. I. Helman and J. P. Kokko
31P-nuclear magnetic resonance (NMR) studies were conducted on split
epithelial sheets of frog skins to examine the effects of hypoxia and
respiratory pH variations on various phosphate-containing intracellular
substrates. Frog skins were split into epithelial sheets from which the
supporting tissue was removed. Epithelial sheets in either phosphate-free
Cl--Ringer or phosphate-free SO2-4-Ringer were bubbled at room temperature
with 100% N2, 100% O2, 2% CO2-98% O2, 5% CO2-95% O2, and 15% CO2-85% O2.
The results show that the intracellular pH (pHi) with Cl- -Ringer was 7.19
and with SO2-4-Ringer was 7.42 with extracellular pH of 7.52 when bubbled
with 100% O2. These pHiS indicate that H+ concentration is at least an
order of magnitude less than predicted from the previously measured Nernst
potential. With exposure to increasing extracellular PCO2, there is a
polynomial decrease in pHi. The pHi tended to be more alkaline in SO2-4
-Ringer, suggesting the presence of a HCO-3/Cl- exchange mechanism. The ATP
concentration is critically and reversibly dependent on PO2. ADP
concentrations were consistently low in well-oxygenated conditions.
Variable but small quantities of phosphocreatine were detected. These
studies demonstrate further the potential importance in utilizing NMR
spectroscopy to examine coupling of biochemical substrates to epithelial
transport processes.
