Effects of temperature and extracellular pH on metabolites: kinetics of anaerobic metabolism in resting muscle by 31P- and 1H-NMR spectroscopy

Abstract

Muscle metabolism is susceptible to a variety of stressing agents affecting particularly the overall rate of energy turnover. As is well known, temperature is a key environmental determinant of the activity of cellular multienzyme systems, such as muscle. In fact, this variable determines the kinetics and flux throughout biochemical pathways, particularly metabolic rates. Another key environmental determinant of cellular multienzyme system activity is intracellular pH. In general, owing to the presence of pH-sensitive ionizing groups, enzymes are active only over a limited range of pH with a definite optimum. Moreover, extracellular acidosis has been shown to play a key role in metabolic processes (Hood et al., 1988). Also, severe hypoxia and anoxia may modulate the ATP demand by the cell (Hochachka, 1986a,b). Skeletal muscle is known to be one of the most hypoxia-tolerant tissues and, in O2-limiting conditions, can survive by means of a metabolic depression, thereby saving substrates and reducing deleterious end-product formation.Ectothermic vertebrates, such as the frog, that normally experience rapid and large variations in body temperature (T) and consequent acid-base state changes, based on physicochemical adaptations (Boutilier, 2001), appear to tolerate such changes with minimal metabolic disturbances. The effects of temperature variations on acid-base balance regulation mechanisms have been well documented (Reeves, 1969). The 'in vivo' blood pH of most studied ectothermic species decreases as temperature increases with a slope close to -0.018·pH·units·°C -1 (Malan et al., 1976). It has been suggested that ∆pH/∆T changes of such an extent can keep the histidine groups of proteins at an almost constant dissociation state (alphastat hypothesis; Reeves, 1972 Environmental stress, such as low temperature, extracellular acidosis and anoxia, is known to play a key role in metabolic regulation. The aim of the present study was to gain insight into the combined temperature-pH regulation of metabolic rate in frog muscle, i.e. an anoxia-tolerant tissue. The rate of exergonic metabolic processes occurring in resting isolated muscles was determined at 15°C and 25°C as well as at extracellular pH values higher (7.9), similar (7.3) and lower (7.0) than the physiological intracellular pH. 31 P and 1 H nuclear magnetic resonance spectroscopy high-resolution measurements were carried out at 4.7·T in isolated frog (Rana esculenta) gastrocnemius muscle during anoxia to assess, by means of reference compounds, the concentration of all phosphate metabolites and lactate. Intra-and extracellular pH was also determined.In the range of examined temperatures (15-25°C), the temperature dependence of anaerobic glycolysis was found to be higher than that of PCr depletion (Q 10 =2.3). High-energy phosphate metabolism was confirmed to be the initial and preferential energy source. The rate of phosphocreatine hydrolysis did not appear to be affected by extracellular pH changes. By contrast, independent of the intracellular pH value, at ...

Detection of lactate with a hadamard slice selected, selective multiple quantum coherence, chemical shift imaging sequence (HDMD‐SelMQC‐CSI) on a clinical MRI scanner: Application to tumors and muscle ischemia

“…A dual-tuned coil approach (such as (38,39)) could compare lactate results to phosphorus spectroscopy to further elucidate this relationship. This would investigate the interaction of lactate, pH, PCr, and other metabolites, as suggested previously by experiments with frog muscle (40). Performing these measurements on humans using clinical scanners will allow for the investigation of muscle energetics in exercise, peripheral vascular disease, muscle ischemia, and other phenomena.…”

Transcatheter closure of a traumatic VSD in an adult requiring an ASD occluder device

“…A dual‐tuned coil approach (such as Boska et al (38) and Pipinos et al (39)) could compare lactate results to phosphorus spectroscopy to further elucidate this relationship. This would investigate the interaction of lactate, pH, phosphocreatine, and other metabolites, as suggested previously by experiments with frog muscle (40). Performing these measurements on humans, using clinical scanners, will allow for the investigation of muscle energetics in exercise, peripheral vascular disease, muscle ischemia, and other phenomena.…”

Tribute to R. G. Boutilier: The role for skeletal muscle in the hypoxia-induced hypometabolic responses of submerged frogs

“…Hypometabolism in sartorius was reversible and repeatable (Feng, 1932), and the excess recovery heat after re-oxygenation was exquisitely responsive to the level of metabolic load imposed on the muscle during anoxia. Recent experiments have further demonstrated that (i) step changes in O 2 availability cause step changes in the stable metabolic heat production of isolated skeletal muscle Boutilier, 2001b) and of the whole animal (Schulz et al, 1991); (ii) the extent of suppression of muscle heat flux (to 20-30% of normal; Fig.·2) matches the reduction in muscle ATP synthesis as well as the anoxia-induced change in whole-animal metabolism (Schulz et al, 1991;West and Boutilier, 1998;Vezzoli et al, 2003;Vezzoli et al, 2004); and (iii) muscle ATP concentration is protected during anoxia. Anaerobic lactate accumulation is relatively low in anoxic sartorius and gastrocnemius (Vezzoli et al, 2004) at rest.…”