Chronic hypoxia delays myocardial lactate dehydrogenase maturation in young rats.

The effect of exposure to hypobaric hypoxia for 4 weeks (oxygen pressure = 106 hPa), equivalent to 5500 m in altitude) on myocardial total lactate dehydrogenase (tLDH) activity and isoform (H and M) composition was comparatively studied in growing (4.5 weeks old) and in adult (4.5 months old) male rats.

Diet restriction plays an important role in the alterations of heart mitochondrial function following exposure of young rats to chronic hypoxia.

Male Wistar rats aged 4 weeks, were subjected to hypobaric hypoxia (barometric pressure 505 hPa, PI,O2 106 hPa) or to diet restriction (reproducing the effect of hypoxia-induced anorexia) for 4 weeks. Each group (control, hypoxic, pair-fed, n = 16), was divided into two sub-groups housed individually in either normal cages or cages with running wheels allowing evaluation of voluntary activity (n = 8 each). The skinned-fibre technique was used to evaluate the functional properties of myofibrillar mitochondria from right and left ventricles in situ.

Differential responses to chronic hypoxia and dietary restriction of aerobic capacity and enzyme levels in the rat myocardium.

Chronic exposure of mammals to hypoxia induces a state of anorexia. We aimed to determine the role played by diet restriction in the alterations of myocardial energy metabolism occurring under chronic hypoxia in order to detect the specific effects of hypoxia per se. Adult female rats were exposed to normobaric hypoxia (FiO2 = 0.

Alteration in the control of mitochondrial respiration by outer mitochondrial membrane and creatine during heart preservation.

Objective: This study aimed to evaluate the nature and extent of mitochondrial alterations during heart preservation.

Methods: Rat hearts, isolated after cardioplegia in situ, were preserved for 6 or 15 h at 4 degrees C either by immersion in cardioplegic solution or by low-flow perfusion (0.3 ml/min) with cardioplegic solution.

Striking differences between the kinetics of regulation of respiration by ADP in slow-twitch and fast-twitch muscles in vivo.

The kinetics of in vivo regulation of mitochondrial respiration by ADP was studied in rat heart, slow-twitch skeletal muscle (soleus) and fast-twitch skeletal muscle (gastrocnemius, plantaris, quadriceps and tibialis anterior) by means of saponin-skinned fibres. Mitochondrial respiratory parameters were determined in the absence and presence of creatine (20 mM), and the effect of proteolytic enzymes (trypsin, chymotrypsin or elastase) on these parameters was investigated in detail. The results of these experiments confirm the observation of Veksler et al.