Blood flow heterogeneity measured by laser-Doppler flowmetry in rabbit skeletal muscles
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(2) Blood flow heterogeneity measured by laser-Doppler flowmetry in rabbit skeletal. muscles Junichi SUZUKI Research and Education Center for Winter Sports, Hokkaido Universiy qf Education, 5-3 Ainosato, Kita-ku, Sapporo, Hokkt do 002-8502, Japan Abstract This study was designed to observe reactive and exercise hyperemia, and to examine blood flow heterogeneity in skeletal muscle surface in rabbit hind-limb using a laser-Doppler flowmeter. After the titanic contraction, the blood flow increased by 48%-365% in the soleus muscle (SOL).In the reactive hyperernia test, the blood flow decreased by 58.9*2.5% and 75.5&1.70/0during 10-sec ischemia, and increased by 38.5*3.0% and 26,1*2.0% after ischemia in the gastrocnemius (GAS) and SOL, respectively. Resting blood flows were 2.0-25.2 (mean 13.0%1.2), 4.0-39.8 ( 19.1*2.T), and 2.9- 14.2 (6.5*0.7) mVmin/lOOg in GAS, SOL. and tibialis anteriole muscle (TA), respectively. The coefficient 0 6 variation of blood flow was greater in SOL (59%) than in both GAS (45%) and TA (44%). These results indicate that this method may be applicable in further studies of microvascular adaptation to physical stress. The results ofresting blood flow suggest that slow twitch fibers have rich distribution of dual-blood flow channels in untrained animals used here.. Key words: blood flow heterogeneity; dual-blood flow channels; exercise hyperemia; laserDoppler flowmeter; reactive hyperernia. Skeletal muscle blood flow has been investigated by venous out flow [7,2 1,231, thennodilution [1,19], hydrogen gas clearance [8,22], microspheres [2] and so on. None of former studies, however, measured blood flow in a muscle surface using a laser-Doppler flowmetry (LDF), which apparatus can measure easily the flow of red blood cells. Further, the spatial heterogeneity of blood flow in in sifu muscle preparation has not been studied using the LDF. In former studies, spatial heterogeneity of blood flow has been observed in hamster [I3], rat [lo], rabbit 1161, cat [4], frog [5,9] and chicken [I31 skclctat muscles. Popel and Dawant [ I 81 postulated that the cause of spatial heterogeneity of blood flow was heterogeneity in angioarchitecture. On the other hand, the blood flow heterogeneity can be accounted For by the dual-circulation hypothesis [1I,23], which proposes the presence of a nutritional (slow flow channel) and shunt (fast flow channel) circulation in the microcirculation of skeletal muscle. According to this theory, the slow and fast flow channcls play an important rolc in maintaining car-. diac output, respectively, at optimal level, even while severe exercise. If the skeletal muscle circulation abounds in these two channels, then resting blood flow within certain muscle tissues would be heterogeneous. The present study was designed to measure reactive and exercise hyperemia to determine whether the LDF is applicable to measure blood flow in the muscle surface. Resting blood flow at different muscle sites was also measured to examine the heterogeneous distribution of blood flow in rabbit hindleg muscles. This study discuss findings in terms of the dual-blood flow theory.. Materials and methods This study was performed in accordance with the "Guiding Principles for the Care and Use of Animals in thc Ficld of Physiological Sciencest'of the Physiological Society of Japan.. Animals and prepamtion Japanese white rabbits weighing 4.4-4.8 kg were used in the present.
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