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This Article Full Text Full Text (PDF) All Versions of this Article: 297/1/H364    most recent 00272.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wüst, R. C. I. Articles by Degens, H. PubMed PubMed Citation Articles by Wüst, R. C. I. Articles by Degens, H.

Region-specific adaptations in determinants of rat skeletal muscle oxygenation to chronic hypoxia

¹Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester; ²Research Institute MOVE, Faculty of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam; ³Department of Pediatrics and ⁴Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen; and ⁵Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands

Submitted 19 March 2009 ; accepted in final form 28 April 2009

Chronic exposure to hypoxia is associated with muscle atrophy (i.e., a reduction in muscle fiber cross-sectional area), reduced oxidative capacity, and capillary growth. It is controversial whether these changes are muscle and fiber type specific. We hypothesized that different regions of the same muscle would also respond differently to chronic hypoxia. To investigate this, we compared the deep (oxidative) and superficial (glycolytic) region of the plantaris muscle of eight male rats exposed to 4 wk of hypobaric hypoxia (410 mmHg, PO₂: 11.5 kPa) with those of nine normoxic rats. Hematocrit was higher in chronic hypoxic than control rats (59% vs. 50%, P < 0.001). Using histochemistry, we observed 10% fiber atrophy (P < 0.05) in both regions of the muscle but no shift in the fiber type composition and myoglobin concentration of the fibers. In hypoxic rats, succinate dehydrogenase (SDH) activity was elevated in fibers of each type in the superficial region (25%, P < 0.05) but not in the deep region, whereas in the deep region but not the superficial region the number of capillaries supplying a fiber was elevated (14%, P < 0.05). Model calculations showed that the region-specific alterations in fiber size, SDH activity, and capillary supply to a fiber prevented the occurrence of anoxic areas in the deep region but not in the superficial region. Inclusion of reported acclimatization-induced increases in mean capillary oxygen pressure attenuated the development of anoxic tissue areas in the superficial region of the muscle. We conclude that the determinants of tissue oxygenation show region-specific adaptations, resulting in a marked differential effect on tissue PO₂.

tissue oxygenation; capillarization; oxidative capacity