The carnosine C-2 proton's chemical shift reports intracellular pH in oxidative and glycolytic muscle fibers.
The appearance of new peaks in the 7.7-8.6 and 6.8-7.4 ppm regions of the postexercise (1)H spectrum of frog muscle is reported. These new peaks result from the splitting of single pre-exercise carnosine C-2 and C-4 peaks into two peaks, representing the intracellular pH (pH(I)) of oxidative and glycolytic fibers. The following data support this conclusion: 1) comparison of means and regression analysis indicates equivalence of the pH(I) measurements by (1)H and (31)P NMR; 2) the pre- and poststimulation concentrations of carnosine are equal; 3) in ischemic rat hindlimb muscles, the presence of a single, more acidic peak in the plantaris; a single, less acidic peak in the soleus; and two peaks (more and less acidic) in the gastrocnemius correspond to published values for the fiber-type composition of these muscles; and 4) in muscles treated with iodoacetate prior to and during stimulation, a second peak never appears. These data indicate that it is feasible to measure separately the pH(I) of oxidative and glycolytic fibers using (1)H NMR spectroscopy.
Damon
Bruce M
BM
Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois, USA. bruce.damon@vanderbilt.edu
Hsu
Alex C
AC
Stark
Heather J
HJ
Dawson
M Joan
MJ
D000818:Animals; D002336:Carnosine / Q000378:metabolism*; D006019:Glycolysis; D006614:Hindlimb; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009682:Magnetic Resonance Spectroscopy; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D011894:Rana pipiens; D051381:Rats
D002336:Carnosine