Correlation of lactate and pH in human skeletal muscle after exercise by 1H NMR

Magn Reson Med. 1991 Jul;20(1):57-65. doi: 10.1002/mrm.1910200107.

Abstract

We have made in vivo 1H NMR measurements of the time course of pH and lactate in human skeletal muscle after exercise. Spectra were obtained in a 4.7-T 30-cm bore Bruker Biospec spectrometer with a 2.5-cm diameter single surface coil. pH was determined from the shift of the endogenous carnosine H-C2 peak while lactate concentrations were determined by comparison with endogenous total creatine, taken to be 28.5 mM/kg wet wt. Fitting the data shows that the exponential decay of lactate (-0.094 +/- 0.014 min-1. t1/2 = 10.6 min) is slower than that of pH (-0.147 +/- 0.015 min-1, t1/2 = 4.7 min), n = 7 with two different volunteers. These values are significantly different with P less than 0.0005. Relaxation times of lactate and creatine were also measured for lactate quantitation; creatine T1, 1.23 +/- 12 s, T2, 136.2 +/- 26.4 ms (both in resting human muscle); lactate T1 (in postmortem rabbit muscle), 1.0 +/- 11 s and T2, 80 ms (in postexercise human muscle). At the end of intense exercise, the lactate level reached was 25.3 +/- 4.0 mM and the average pH drop was 1.0 pH unit. We discuss the implications of these measurements in conjunction with existing data on other sources of H+ flux, phosphocreatine resynthesis, H+ transport, and contribution of inorganic phosphate to buffering.

MeSH terms

  • Adult
  • Carnosine / pharmacokinetics
  • Creatine / pharmacokinetics
  • Fatigue / metabolism
  • Humans
  • Hydrogen
  • Hydrogen-Ion Concentration
  • Lactates / pharmacokinetics*
  • Magnetic Resonance Spectroscopy* / methods
  • Male
  • Muscles / metabolism*
  • Physical Endurance
  • Physical Exertion*
  • Time Factors

Substances

  • Lactates
  • Hydrogen
  • Carnosine
  • Creatine