Determination of human skeletal muscle buffer value by homogenate technique: methods of measurement

Abstract

The human muscle buffer value (beta) is most frequently determined by either fixed acid titration of a homogenate ["in vitro" beta (beta vit)] or measurement of the change in lactate concentration (delta [La]) relative to the change in muscle homogenate pH after high-intensity exercise ["in vitro" beta = - delta [La]/delta pH (beta viv)]. We sought to compare beta viv, determined after isometric and dynamic exercise to exhaustion (approximately 60 s), with beta vit. Resting (R) and postexercise (E) biopsy samples were taken from vastus lateralis muscles of 43 human volunteers. Freeze-dried muscle was homogenized (30 mg/ml) in NaF (0.01 M) for the measurement of muscle pH (R and E). beta vit was determined by HCl (0.01 M) titration of the homogenate over the pH range 7.1-6.5. Muscle lactate was measured by enzymatic assay. There was no significant difference between beta viv determined after isometric (n = 35) or dynamic (n = 8) exercise to fatigue (170 vs. 168 mmol H+.kg dry muscle mass-1.pH-1, respectively; P > 0.05). Values for beta vit in the corresponding muscle samples (R) were approximately 7-8% lower (156 +/- 25 vs. 157 +/- 18 mmol H+.kg dry muscle mass-1.pH-1, respectively). There was no significant difference (P = 0.278) between the measured decline in muscle homogenate pH after exercise and the reduction in pH predicted from beta vit and delta [La], indirectly confirming the lack of any significant difference between beta viv and beta vit.(ABSTRACT TRUNCATED AT 250 WORDS)

High Level of Skeletal Muscle Carnosine Contributes to the Latter Half of Exercise Performance during 30-s Maximal Cycle Ergometer Sprinting.

“…This difference was probably due to the water content in biopsy samples. Because the mean water content in the samples at rest is 77.9Ϯ1.7%, 1 mmol · kg Ϫ1 of dry muscle mass is equal to 0.23 mmol · kg Ϫ1 of wet muscle mass [21]. Based on this finding, when the carnosine concentration in wet muscle in the present study was converted into that in dry muscle, it equaled 15.9 mmol · kg…”

Effects of high-intensity training on muscle lactate transporters and postexercise recovery of muscle lactate and hydrogen ions in women

“…2). This result is likely to be due to a decrease in the intracellular buffers that are measured using the in vitro titration technique (i.e., phosphate, protein, and dipeptides within the muscle) (33). Our previous research (15) indicates that a decrease in muscle carnosine content is not the cause of the decrease in ␤m in vitro .…”

A-769662 activates AMPK β1-containing complexes but induces glucose uptake through a PI3-kinase-dependent pathway in mouse skeletal muscle

“…Estimation of free ADP and AMP concentrations was based on the near-equilibrium nature of the Cr phosphokinase and adenylate kinase reactions using the equilibrium constants 1.66 ϫ 10 9 and 1.05, respectively (27). Free ADP was estimated from the measured ATP, Cr, and PCr and H ϩ content, and the H ϩ concentration was estimated from the lactate content as previously described (32).…”