The carnosine C-2 proton's chemical shift reports intracellular pH in oxidative and glycolytic muscle fibers

• Published in: Magnetic resonance in medicine Vol. 49; no. 2; pp. 233 - 240
• Main Authors: Damon, Bruce M., Hsu, Alex C., Stark, Heather J., Dawson, M. Joan
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 01.02.2003; Williams & Wilkins
• Subjects: Animals; Biological and medical sciences; Carnosine - metabolism; exercise; fiber types; Glycolysis; Hindlimb; Hydrogen-Ion Concentration; In Vitro Techniques; Investigative techniques, diagnostic techniques (general aspects); Isometric Contraction; Magnetic Resonance Spectroscopy; Medical sciences; Muscle Fibers, Fast-Twitch - metabolism; Muscle Fibers, Slow-Twitch - metabolism; Muscle, Skeletal - metabolism; nuclear magnetic resonance; Osteoarticular system. Muscles; Oxidation-Reduction; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Rana pipiens; Rats; skeletal muscle; Animal model; fiber types; Frog; Amphibia; Cardiovascular disease; exercise; Salientia; Glycosylation; NMR spectrometry; Case control study; Muscular fiber; Experimental study; Soleus muscle; nuclear magnetic resonance; Vertebrata; Ischemia; Measurement technique; Animal; hydrogen-ion concentration; Dipeptides; Proton; pH; Oxidation; skeletal muscle
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.10384

The appearance of new peaks in the 7.7–8.6 and 6.8–7.4 ppm regions of the postexercise 1H 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 (pHI) of oxidative and glycolytic fibers. The following data support this conclusion: 1) comparison of means and regression analysis indicates equivalence of the pHI measurements by 1H and 31P 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 pHI of oxidative and glycolytic fibers using 1H NMR spectroscopy. Magn Reson Med 49:233–240, 2003. © 2003 Wiley‐Liss, Inc.