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Non‐P i buffer capacity and Initial phosphocreatine breakdown and resynthesis kinetics of human gastrocnemius/soleus muscle groups using 0.5 s time‐resolved 31 P MRS at 4.1 T
Author(s) -
Newcomer Bradley R.,
Boska Michael D.,
Hetherington Hoby P.
Publication year - 1999
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/(sici)1099-1492(199912)12:8<545::aid-nbm595>3.0.co;2-j
Subject(s) - phosphocreatine , pi , chemistry , soleus muscle , gastrocnemius muscle , kinetics , biceps , medicine , bicarbonate , endocrinology , anatomy , energy metabolism , biology , skeletal muscle , physics , biochemistry , organic chemistry , quantum mechanics
High‐time‐resolution (0.5 s) 31 P MRS has been used to evaluate the initial phosphoreatine (PCr) breakdown and resynthesis kinetics, to calculate the non‐P i /non‐bicarbonate buffer capacity (βnon‐P i /non‐bicarb ), and to calculate the constant relating the change in intracellular pH to the muscle's H + efflux rate (λ). The slope of PCr vs time demonstrates that a slope calculated using the first 10 s of recovery underestimates initial PCr recovery rates by up to 56%. A 1–2 s time window is needed to produce a slope that is statistically equivalent to the slope measured using a 0.5 s time window ( p = 0.008, one‐way RM‐ANOVA, Student–Newman–Keuls multiple comparison test). In addition, there was no delay or acceleration in PCr recovery after a 90 s maximum voluntary contraction (MVC) in normal subjects. This demonstrates that oxidative metabolism is occurring at the end of a 90‐s MVC in normal individuals. Fitting recovery data has determined that βnon‐P i /non‐bicarb = 24.3 ± 5.4 slyke (mmol/L/pH unit) and that λ = 0.129 ± 0.077 m M /(ph s) for human gastrocnemius/soleus muscle. βnon‐P i /non‐bicarb is in agreement with measurements in cat biceps, cat soleus and rat gastrocnemius muscles. Copyright © 1999 John Wiley & Sons, Ltd.