Moderate-intensity exercise training with low concentration Co2+ treatment did not affect muscle capillarity and oxidative capacity in rats

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(1)Title. Moderate-intensity exercise training with low concentration Co2+ treatment did not affect muscle capillarity and oxidative capacit y in rats. Author(s). 鈴木, 淳一. Citation. 冬季スポーツ研究, 4(1): 7-16. Issue Date. 2002-03. URL. http://s-ir.sap.hokkyodai.ac.jp/dspace/handle/123456789/6781. Rights. Hokkaido University of Education.

(2) Moderate-intensity exercise training with low concentration. co2+treatment. did not affect muscle capillarity and oxidative capacity in rats Junichi SUZUKE. Research and Education Center for Winter Sporrs, Hokkaido University of Educaiion, 5-3Ainosaro, Kita- ku, Sapporo, Ho kkido 002-8502, Japan Abstract This study was designed to examine the changes in the capillary geometry, especially the distribution of arteriolar and venular capillaries, in skeletal musc tes after endurance training with chronic CoCI2 administration in male SD rats. Exercise training by running lasted for 8 weeks at 25 rnJmin on a 0-10% gradient, 15-30 midday, 3 days per week. Morphological findings were obtained from soleus (SOL), deep portion of plantaris (PL) and anterior costal region of diaphragm (Dl A) muscles. The co2' adrninistration significantly increased blood RBC concentration by around 20% irrespective of training condition. Total capillary density and the density of arteriolar capillaries tended to increase, but not significant, in PL after the training with co2' administration. Both training and C O administration ~ ~ significantly decreased the capillary-to-fiberratio (C:F) in the PL (P<0.05).In SOL and DIA, the C:F remained unchanged after either training or co2' administration- The training atone significantly increased the FCSA of type IIa fiber in SOL (W0.05).The proportion of each Fiber type did not change after either training or co2'administration in all muscle portions exarnined. The exercise training significantly increased the SDH activity of type 1 fiber in SOL (P<O.OS). In contrast, CO* administration tended to decrease the SDH.These results suggest that a moderate-intensity endurance training with CO" administration does not improve muscle microvascular network. '. Key. words: angiogenesis; cobalt; endurance training; skeletal muscle; succinate dehydre-. genase. Recently, the altitude training, i .e., exercise training under hypoxic condition has been used to improve endurance performance [for a review; 41. One of the most documented physiological adaptation to a reduced PIol is the increased release of erythropoietin (EPO), which causes a transient increase in the RBC concentration [38]. This hypoxia-induced polycythemia is induced primary by an expression of hypoxia inducible factor, known as HIF, in response to hypoxic stimuli [18,19]. The HIF stimulates an expression of vascular endothelial growth factor (VEGF) as well as a production of EPO (91. It is therefore possible that chronic exposure to hypoxia improve rnus~lecapillarity. However, hypoxia exposure alone fstcil itates microvascular remodell ings in skeletal muscle remained equivocal [3,11,35]. Numerous studies have shown that endurance exercise training induces a marked increase in cap-. illarity in skeletal muscles [e.g. 231. While the regulating mechanisms in exercise-induced angiogenesis have not been clearly understood, reduced oxygen tension 12,501 andtor mechanical factors, such as shear stress and tissue stretching [l0,53] may stimulate expression of peptide angiogenic factors, including VEGF. It seems possible that exercise training under chronic hypoxic condition further facilitates exercise-induced microvascular remodeling~. It has been reported that acute single bout exercise under hypoxic condition further augmented VEGF mRNA response in rat skeletal muscle 181. In contrast, human study failed to show any further increase in VEGF mRNA expression after acute exercise either with blood flow-restriction [22] or hypoxic breathing [36]. Endurance training at simulated high altitude induced a non-significant increase in muscle capillarity in humans [47] and.

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