Quantifying H+ exchange from muscle cytosolic energy catabolism using metabolite flux and H+ coefficients from multiple competitive cation binding: New evidence for consideration in established theories

Abstract

The purpose of this investigation was to present calculations of fractional H+ exchange (~H+e) from the chemical reactions of non-mitochondrial energy catabolism. Data of muscle pH and metabolite accumulation were based on published research for intense exercise to contractile failure within ~3 min, from which capacities and time profiles were modeled. Data were obtained from prior research for multiple competitive cation dissociation constants of metabolites and the chemical reactions of non-mitochondrial energy catabolism, and pH dependent calculations of ~H+e from specific chemical reactions. Data revealed that the 3 min of intense exercise incurred a total ATP turnover of 142.5 mmol L−1, with a total intramuscular ~H+ exchange (-‘ve = release) of −187.9 mmol L−1. Total ~H+ metabolic consumption was 130.6 mmol L−1, revealing a net total ~H+e (~H+te) of −57.3 mmol L−1. Lactate production had a ~H+te of 44.2 mmol L−1 (for a peak accumulation = 45 mmol L−1). The net ~H+te for the sum of the CK, AK, and AMPD reactions was 36.33 mmol L−1. The ~H+te from ATP turnover equaled −47.5 mmol L−1. The total ~H+ release to lactate ratio was 4.3 (187.9/44). Muscle ~H+ release during intense exercise is up to ~4-fold larger than previously assumed based on the lactic acid construct.