Hypoxia-induced fibre type transformation in rat hindlimb muscles

Abstract

Twelve male Sprague-Dawley rats (21 days old) were randomly assigned into two experimental groups: sea level control (CONT) and hypobaric hypoxia (HYPO). The HYPO rats were kept in an hypobaric chamber maintaining a simulated altitude of 4000 m (61.1 kPa). After 10 weeks of treatment, the rat hindlimb muscles [soleus (SOL) and extensor digitorum longus (EDL)] were subjected to histochemical and electro-mechanical analyses. Results indicated that compared to CONT the HYPO SOL muscle had a significantly greater relative distribution of fast-twitch-oxidative-glycolytic (FOG) fibres (28.9% SEM 2.0 vs 18.3% SEM 1.8, P less than 0.01) with a significant decrease in slow twitch oxidative fibre distribution (69.5% SEM 2.4 vs 82.9% SEM 3.1, P less than 0.01). Compared to CONT the HYPO EDL muscle also manifested a significant increase in FOG fibre distribution (51.6% SEM 0.8 vs 46.6% SEM 1.1, P less than 0.01), but this was accompanied by a significant decrease in fast twitch glucolytic fibres (44.3% SEM 0.9 vs 49.2% SEM 1.7, P less than 0.05). These histochemical fibre type transformations accompanied significant and expected changes in the electro-mechanical parameters tested in situ, e.g. maximal twitch force, maximal rate of force development, contraction time, half relaxation time, force: frequency curve, and fatigability. It was concluded that chronic hypobaric hypoxia could have a potent influence upon the phenotype expression of muscle fibres.

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

“…Alterations in the number of MCT-4 transporters may potentially explain the adaptive change occurring during a long acclimatization period. This might be in accordance with the observation (Itoh et al, 1990) in rat muscles exposed to simulated altitude (4000·m) for a long period (10·weeks), of a significant increase in the percentage of type II fibres, the only ones able to express MCT-4 in mammals (Bonen, 2001;Fishbein et al, 2002).…”

Fibre types in skeletal muscles of chronic obstructive pulmonary disease patients related to respiratory function and exercise tolerance

“…It has been shown that in various animal species, including humans, both low oxygen availability [9] and disuse [10,11] induce a change in fibre type from slow to fast. We can put forward the hypothesis that in COPD patients either the scarce oxygen availability and/or the inactivity and physical deconditioning cause a fibre transformation with an increase in the proportion of fast fatiguable fibres.…”

“…Muscle training improves tolerance to exercise without actual improvement of pulmonary mechanics or gas exchange [7]. A shift of the lactate threshold is likely to play a role [7], possibly in relation to an improvement of oxidative potential [8].It has been shown that in various animal species, including humans, both low oxygen availability [9] and disuse [10,11] induce a change in fibre type from slow to fast. We can put forward the hypothesis that in COPD patients either the scarce oxygen availability and/or the…”

General – Circulation

“…They also suggest that in both cases, the vasoconstriction is predominantly due to the release of noradrenaline and that a small component is due to ATP. Whether chronic hypoxia causes angiogenesis and/or affects muscle fibre type and size is controversial (Banchero, 1987;Itoh et al 1990;Abdelmalki et al 1996). However, in recent studies we provided some evidence that chronic 145P hypoxia of up to 3 weeks does cause a progressive increase in branching density at the arteriolar level in spinotrapezius (Smith & Marshall, 1997) and at the capillary level in diaphragm and soleus, but not in extensor digitorum longus (EDL) (Deveci et al 1998) muscle of the rat.…”