Behnke Bradley J, Prisby Rhonda D, Lesniewski Lisa A, Donato Anthony J, Olin Hillary M, Delp Michael D
Division of Exercise Physiology, Department of Physiology and Pharmacology, and the Center for Interdisciplinary Research in Cardiovascular Sciences, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
J Physiol. 2006 Sep 1;575(Pt 2):617-26. doi: 10.1113/jphysiol.2006.108431. Epub 2006 Apr 27.
Key structural and functional properties of the skeletal muscle vasculature that underlie diminished vascular conductance with ageing remain obscure. The purpose of this investigation was to test the hypotheses that (1) reduced levels of spontaneous physical activity in old rats are associated with skeletal muscle vascular remodelling (e.g. arterial rarefaction), and (2) consequent to a vascular remodelling, calculated shear stress is maintained in feed arteries of aged muscle at levels commensurate with that in young. Activity during daily light and dark cycles (12-12 h) was measured at 30-s intervals for 2 weeks in young (6 months; n = 9) and old (24 months; n = 9) Fisher 344 rats via telemetry. Subsequently, the gastrocnemius complex and soleus muscles were excised and all feed arteries were counted, isolated, cannulated and maximally dilated for measurement of luminal diameter. Resting blood flow was also measured to estimate vessel wall shear-stress in the feed arteries perforating the soleus and gastrocnemius muscles. Overall, young rats were approximately 1.6 times more active during dark periods and approximately 4 times more active during light periods than old rats. In addition, young rats had approximately one additional feed artery perforating both the soleus (young, 3.3 +/- 0.2; old, 2.6 +/- 0.2 vessels; P < 0.05) and gastrocnemius (young, 8.8 +/- 0.1; old, 7.5 +/- 0.2 vessels, P < 0.05) muscles compared with old rats. However, average vessel wall shear stress at rest was similar between young and old rats (soleus: Y, 65 +/- 5; O, 64 +/- 5 dynes cm(-2); gastrocnemius: Y, 329 +/- 22; O, 327 +/- 27 dynes cm(-2)) resulting from a larger vessel diameter in arteries from old rats. In conclusion, lower activity levels of old rats likely contribute to resistance artery rarefaction and, consequently, this provides a plausible mechanism for the altered blood flow patterns observed during exercise in aged skeletal muscle.
骨骼肌血管系统关键的结构和功能特性是导致血管传导随衰老而降低的基础，但仍不清楚。本研究的目的是检验以下假设：（1）老年大鼠自发体力活动水平降低与骨骼肌血管重塑（如动脉稀疏）有关；（2）血管重塑后，老年肌肉供血动脉中的计算剪切应力维持在与年轻肌肉相当的水平。通过遥测技术，对年轻（6个月；n = 9）和老年（24个月；n = 9）的费希尔344大鼠在每日光照和黑暗周期（12 - 12小时）内，每隔30秒测量一次活动情况，持续2周。随后，切除腓肠肌复合体和比目鱼肌，对所有供血动脉进行计数、分离、插管并最大程度扩张以测量管腔直径。还测量了静息血流，以估计穿过比目鱼肌和腓肠肌的供血动脉中的血管壁剪切应力。总体而言，年轻大鼠在黑暗期的活动量约为老年大鼠的1.6倍，在光照期约为4倍。此外，与老年大鼠相比，年轻大鼠在比目鱼肌（年轻，3.3±0.2；老年，2.6±0.2条血管；P < 0.05）和腓肠肌（年轻，8.8±0.1；老年，7.5±0.2条血管，P < 0.05）中分别多约一条供血动脉。然而，年轻和老年大鼠静息时的平均血管壁剪切应力相似（比目鱼肌：年轻，65±5；老年，64±5达因/厘米²；腓肠肌：年轻，329±22；老年，327±27达因/厘米²），这是由于老年大鼠动脉的血管直径较大。总之，老年大鼠较低的活动水平可能导致阻力动脉稀疏，因此，这为老年骨骼肌运动期间观察到的血流模式改变提供了一种合理的机制。
