Proton efflux from rat skeletal muscle in vivo: changes in hypertension

Abstract

1. An analysis of the recovery kinetics of intracellular pH and phosphocreatine concentration after exercise in skeletal muscle was developed to calculate the rate of proton efflux in vivo. 2. Recovery of rat leg muscle pH after sciatic nerve stimulation was faster in spontaneously hypertensive rats than in Wistar-Kyoto controls (both n = 5). 3. Analysis of these data showed that the rate of proton efflux depends on intracellular pH, being greater at lower pH. 4. The early rate of proton efflux was greater in spontaneously hypertensive rats [measured over the first 0.8 min, 12.5 mmol min-1 kg-1 (SEM 1.8) in spontaneously hypertensive rats compared with 7.6 mmol min-1 kg-1 (SEM 0.4) in Wistar-Kyoto rats, P less than 0.05], even though pH at the start of recovery was higher [6.30 (SEM 0.03) in spontaneously hypertensive rats compared with 6.17 (SEM 0.01) in Wistar-Kyoto rats, P less than 0.01]. 5. This novel analysis provides a quantitative estimate of the rate of proton efflux in vivo, and demonstrates directly that this is increased in spontaneously hypertensive rats, as has previously been inferred from pH changes during exercise and studies of cultured muscle cells in vitro.

ATP production and mechanical work in exercising skeletal muscle: A theoretical analysis applied to 31P magnetic resonance spectroscopic studies of dialyzed uremic patients

“…The initial proton efflux rate was calculated from pH and [PCr] in the end-exercise and first-recovery spectra (Eq. [4]). As this has an approximate linear pH-dependence (4,7,8), the proton efflux rate was divided by the difference between resting and end-exercise pH to calculate an efflux rate constant (Eq.…”

“…As this has an approximate linear pH-dependence (4,7,8), the proton efflux rate was divided by the difference between resting and end-exercise pH to calculate an efflux rate constant (Eq. 151) (4,12); this rate constant is taken as an estimate of the pH-dependence of proton efflux during exercise (12).…”

“…Exercise in which the workload is incremented sequentially (e.g., (2,3)) can accommodate a wide range of exercise performance, while achieving a similar end-exercise state in patients and controls. This facilitates the analysis of PCr and pH recovery, which can be used to estimate effective mitochondrial capacity QMAX, and rates of effective proton efflux (4)(5)(6)(7)(8). Furthermore, measurements of pH during mixed (i.e., oxidative and glycolytic) exercise can detect abnormalities of glycogenolysis and/or proton efflux (2, 7 , 9).…”

Effect of Parathyroid Hormone on Rat Skeletal Muscle in vivo

“…To allow for possible differences in end-exercise pH, we divided the initial proton efflux rate by the end-exercise fall in pH below its rest ing value, producing an apparent first-order efflux rate constant [22], Results are presented as mean values ± SEM. Differences in exercise time course data were assessed using repeated-measures analysis of variance.…”

“…To assess effective rates of proton efflux during pH recovery after exercise, we used a calculation based on the release of protons by PCr synthesis and from the passive buffers of the cell [20][21][22], using data from the end-exercise and first two recovery spectra (t = 0-0.47 min). To allow for possible differences in end-exercise pH, we divided the initial proton efflux rate by the end-exercise fall in pH below its rest ing value, producing an apparent first-order efflux rate constant [22], Results are presented as mean values ± SEM.…”