The viability of small whole muscles after incubation in vitro : a reply

1. We examined the isolated mouse skeletal-muscle model in vitro, commonly used by many investigators, for its suitability for metabolic studies. 2. Despite the fact that pH, O2 saturation, osmolality and the release of the enzyme creatine kinase remained stable, histochemical studies showed large cores devoid of glycogen, suggesting that the incubated muscle had lost its viability. 3. This study indicates that caution should be exercised when interpreting the results of studies with intact isolated mouse muscles.

Section: Discussionsupporting

confidence: 64%

Section: Discussionsupporting

confidence: 52%

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Use of the intact mouse skeletal-muscle preparation for metabolic studies. Evaluation of the model

Breda

Keizer

Glatz

et al. 1990

“…Therefore, only the pH criterion suggests directly that the physiological state of the superfused muscles (during the experiment ex vivo) depends on the muscle weight or thickness. However, in fasted animals, our data do not support the previous hypothesis [9][10][11] suggesting that the development of an anoxic core depends on the metabolic rate of the animals: the stability of superfused muscles appeared only to correlate with the muscle size and not with the metabolic rate of starved rats.…”

Section: Discussioncontrasting

confidence: 99%

“…The major concern with the integrity of these muscle preparations is the adequacy of nutrient exchange by diffusion in the absence of a circulatory system. The diffusion is dependent on the tissue thickness, the metabolic rate of the donor animal and the temperature of the buffer solution, which can influence substrate and 02 diffusion into muscle cells and induce a core formation with a loss of glycogen [9][10][11]. The stability of isolated skeletal muscle has been assessed up to now by different criteria: (1) biochemical parameters such as the stability of phosphorylated metabolite levels, glycogenolysis rate and glucose transport, [3,9], (2) physiological parameters, such as the non-impairment of contractile properties during incubation [12] and the protein synthesis rate [10,13], and (3) morphological parameters as defined by histochemistry [10,14,15].…”

Section: Introductionmentioning

confidence: 99%

Use of superfused rat skeletal muscle for metabolic studies: assessment of pH by 31P n.m.r

Meynial-Denis

Mignon

Foucat³

et al. 1993

We developed a muscle superfusion system suitable for metabolic studies of small isolated rat muscle ex vivo in real time and in a non-destructive manner by n.m.r. spectroscopy. In order to determine biochemical stability of superfused extensor digitorum longus (EDL) muscle (from fasted 45 and 100 g rats), the energy state and the pH of muscle were continuously monitored by 31P n.m.r. spectroscopy. ATP and phosphocreatine remained stable during 2 h whatever the muscle size (20 or 45 mg). Neither metabolite was a sensitive probe of possible metabolic compartmentation within muscle under our experimental conditions. By contrast, the chemical shift of Pi by its sensitivity to pH was a discriminant factor in the assessment of muscle stability. Indeed, heterogeneity of pH was observed only in the 45 mg EDL muscle resulting from a core region with loss of glycogen. Together, these observations suggest deviations of energy metabolism to supply ATP. Consequently, pH may be considered as a new real-time criterion for monitoring a metabolic heterogeneity due to changes in energy metabolism of muscle preparations ex vivo.

Long-term treatment of isolated rat soleus muscle with phorbol ester leads to loss of contraction-induced glucose transport

Cleland

Abel

Rattigan

et al. 1990

Muscle contraction involves mobilization of intracellular Ca2+ and is associated with several metabolic adjustments, including increased glucose transport. In the present study isolated rat soleus muscles were exposed to 12-O-tetradecanoylphorbol 13-acetate, and responses to both insulin and contraction in terms of glucose transport were assessed. Muscles treated with this phorbol ester for 12 h showed an increased basal rate of 3-O-methylglucose uptake, and responded partially to insulin but did not respond to contraction. Phorbol-ester-treated and non-treated (vehicle-only) muscles were indistinguishable in terms of pre-contraction content of adenine nucleotide, phosphocreatine, lactate and glycogen, as well as contractile performance and contraction-induced glycogenolysis. Phorbol ester treatment of isolated solei for 12 h resulted in the loss of 90% of protein kinase C activity as determined with histone IIIs as substrate, and 70% as determined by using phorbol ester binding. It is concluded that treatment of solei with phorbol ester gives rise to a marked loss of contraction-induced glucose transport.