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ABSTRACT: Programs of intermittent hypobaric hypoxia (IHH) exposure are used to raise hemoglobin concentration and erythrocyte mass. Although acclimation response increases blood oxygen transport capacity leading to a VO(2max) increase, the effects of reactive oxygen species (ROS) might determine the behavior of erythrocytes and plasma, thus causing a worse peripheral blood flow. The goals of the study were to establish the hematological changes and to discern whether an IHH protocol modifies the antioxidant/pro-oxidant balance in laboratory rats.
Male rats were subjected to an IHH program consisting of a daily 4-hour session for 5 days/week until completing 22 days of hypoxia exposure in a hypobaric chamber at a simulated altitude of 5000 m. Blood samples were taken at the end of the exposure period (H) and at 20 (P20) and 40 (P40) days after the end of the program, and compared to control (C), maintained at sea-level pressure. Hematological parameters were measured together with several oxidative stress indicators: plasma thiobarbituric acid reactive substances (TBARS) and erythrocyte catalase (CAT) and superoxide dismutase (SOD).
Red blood cell (RBC) count, hemoglobin concentration and hematocrit were higher in H group as compared to all the other groups (p < 0.001). However, there were no significant differences between the 4 groups in any of the oxidative stress-related parameters.
The absence of significant differences between groups indicates that our IHH program has little impact on the general redox status, even in the laboratory rat, which is more sensitive to hypoxia than humans. We conclude that IHH does not increase oxidative stress.
Wilderness and Environmental Medicine 12/2010; 21(4):325-31. · 0.94 Impact Factor
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ABSTRACT: Intermittent hypobaric hypoxia (IHH) exposure induces a rise in hemoglobin concentration and an increase in erythrocyte mass in both rats and humans. Although this response increases blood oxygen transport capacity, paradoxically, it could impair blood flow and gas exchange because of the blood viscosity alterations associated with the rising hematocrit. In the present study, male rats were subjected to an IHH program consisting of a daily 4-h session for 5 days/week until they had completed 22 days of hypoxia exposure in a hypobaric chamber at a simulated altitude of 5000 m. Blood samples were taken at the end of the exposure period (H) and at 20 (P20) and 40 (P40) days after the end of the program and were compared to control (C) maintained at sea- level pressure. Apparent blood viscosity (eta(a)) and plasma viscosity (eta(p)) were measured in a cone-plate microviscometer. Although the hematocrit significantly increased in the H group, blood apparent viscosity did not differ among groups, ranging from 7.67 to 6.57 mPa*sec at a shear rate of 90 sec(-1). Relative blood viscosity showed a clear increase (about 27%) in H rats, mainly due to the significant decrease in plasma viscosity. This finding could be interpreted as a compensatory response, which reduced the effect of increased erythrocyte mass volume on whole-blood viscosity. Oxygen delivery index and blood oxygen potential transport capacity remained unchanged in all groups. These data indicate that the IHH program has a deep but transitory effect on red cell parameters and a moderate effect on blood rheological behavior.
High altitude medicine & biology 01/2009; 10(3):275-81. · 1.58 Impact Factor
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ABSTRACT: Adult male Sprague-Dawley rats were randomly assigned to two groups: control and anaemic. Anaemia was induced by periodical blood withdrawal. Extensor digitorum longus and soleus muscles were excised under pentobarbital sodium total anaesthesia and processed for transmission electron microscopy, histochemical and biochemical analyses. Mitochondrial volume was determined by transmission electron microscopy in three different regions of each muscle fibre: pericapillary, sarcolemmal and sarcoplasmatic. Muscle samples sections were also stained with histochemical methods (SDH and m-ATPase) to reveal the oxidative capacity and shortening velocity of each muscle fibre. Determinations of fibre and capillary densities and fibre type composition were made from micrographs of different fixed fields selected in the equatorial region of each rat muscle. Determination of metabolites (ATP, inorganic phosphate, creatine, creatine phosphate and lactate) was done using established enzymatic methods and spectrophotometric detection. Significant differences in mitochondrial volumes were found between pericapillary, sarcolemmal and sarcoplasmic regions when data from animal groups were tested independently. Moreover, it was verified that anaemic rats had significantly lower values than control animals in all the sampled regions of both muscles. These changes were associated with a significantly higher proportion of fast fibres in anaemic rat soleus muscles (slow oxidative group = 63.8%; fast glycolytic group = 8.2%; fast oxidative glycolytic group = 27.4%) than in the controls (slow oxidative group = 79.0%; fast glycolytic group = 3.9%; fast oxidative glycolytic group = 17.1%). No significant changes were detected in the extensor digitorum longus muscle. A significant increase was found in metabolite concentration in both the extensor digitorum longus and soleus muscles of the anaemic animals as compared to the control group. In conclusion, hypoxaemic hypoxia causes a reduction in mitochondrial volumes of pericapillary, sarcolemmal, and sarcoplasmic regions. However, a common proportional pattern of the zonal distribution of mitochondria was maintained within the fibres. A significant increment was found in the concentration of some metabolites and in the proportion of fast fibres in the more oxidative soleus muscle in contrast to the predominantly anaerobic extensor digitorum longus.
Journal of Anatomy 07/2008; 212(6):836-44. · 2.37 Impact Factor
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ABSTRACT: Three groups of sedentary male rats were exposed to intermittent hypobaric hypoxia (IHH) for 22 days (4 h/day, 5 days/week) in a hypobaric chamber at a simulated altitude of 5,000 m. Tibialis anterior (TA) and diaphragm (DG) were removed at the end of the programme (H group), and 20 or 40 days later (P20 and P40 groups). A control group (C) was maintained at sea-level pressure and their TA and DG were compared to those of the experimental rats at the end of the IHH programme, and also 20 and 40 days later. We measured the fibre morphometry and capillaries of each muscle. Our results demonstrate that IHH does not change the fibre type composition (with reference to either their contractile or oxidative properties) for most muscle regions of the muscles analysed analysed. We found few significant differences in muscle capillarity and fibre morphometry for TA after IHH. However, IHH did induce some statistically significant changes in DG: capillary density of the H rats (736 capillaries/mm2) increased compared to C animals (610 capillaries/mm2). Although IHH did not change the fibre capillarization or morphometric parameters of fast fibre types, we observed reductions ranging from 7 to 13% in fibre area, perimeter and diffusion distances between C and H for slow fibres. Moreover, these morphometric changes accounted for increases of 10-20% in capillarization, fibre unit area and fibre unit perimeter. This indicates that SO fibres are more sensitive to IHH than both fast fibre types.
Arbeitsphysiologie 06/2008; 103(2):203-13. · 2.15 Impact Factor
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ABSTRACT: As in humans, the haemoglobin concentration rise and erythrocyte mass increase are the most significant of the haematological adaptive changes induced by intermittent hypobaric hypoxia exposure (IHHE) in rats. Although this response is oriented to increase oxygen transport capacity, paradoxically, the increasing blood capacity could impair peripheral and respiratory gas exchange function because of the blood viscosity alterations associated to the rising haematocrit. The IHHE programme was performed into a hypobaric chamber (5000 m) consisting in daily 4-h sessions, during 5 days per week until completing 22 days of hypoxia exposure. Blood samples were taken at the end of the exposure period (IHHE group), 20 (Post20d) and 40 (Post40d) days after the end of the programme and compared to matched control groups (Control). Apparent blood viscosity (ha) and plasma viscosity (hp) were measured in a cone-plate microviscometer. In addition, relative blood viscosity (ha/Hp), oxygen delivery index (ODI = Hc/h), blood oxygen potential transport capacity (BOTC = β[Hb]/h) and haematological parameters were evaluated. Although the increased haematocrit, blood apparent viscosity does not differs among the different groups. However, relative blood viscosity showed a clear increase in IHHE rats, mainly due to the significant decrease in plasma viscosity detected in this group. This finding could be interpreted as a compensatory response, in order to reduce the impact of red cell mass increased volume on whole blood viscosity. ODI and BOTC remained unchanged between all groups. These data indicate that IHEE programme has a deep but transitory effect on red cell parameters and a very moderate impact on blood rheological behaviour.
Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 04/2007; 146(4 (Supplement)):S164. · 2.23 Impact Factor
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ABSTRACT: We examined the effect of intermittent hypobaric hypoxia exposure (IHHE) in some biochemical markers of aerobic/anaerobic metabolism such as lactate dehydrogenase (LDH), citrate synthase (CS), and myoglobin (Mb) in three different morphofunctional muscles: myocardium (MYO), diaphragm (DFG) and tibialis anterior (TA).
The IHHE programme was performed into a hypobaric chamber (5000 m simulated altitude) consisting in daily 4-h sessions, during 5 days per week until completing 22 days of hypoxia exposure. Samples were taken at the end of the exposure period (IHHE group), 20 (POST20d) and 40 (POST40d) days after the end of programme and compared to a control group (CONT).
LDH activity was significantly depressed in the MYO of IHHE, POST20d and POST40d groups compared with CONT. A reverse tendency was detected in TA muscle, but this increase was non-significant. No differences were found in DFG. Although, any modification was significant, CS showed an opposed trend to LDH, as expected, in all muscles. All muscles showed a trend to increase in Mb concentration, but only in exposed MYO these changes were significant.
These results seem to indicate that morphofunctional modifications due to hypoxia in striated muscles are related not only to oxidative character but also to the degree of muscle activity along the IHHE program.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 04/2007; 146(4 (Supplement)):S184. · 2.20 Impact Factor
