Russell John A, Kindig Casey A, Behnke Brad J, Poole David C, Musch Timothy I
Department of Kinesiology, Kansas State University, Manhattan, KS 66506-5802, USA.
Am J Physiol Heart Circ Physiol. 2003 Jul;285(1):H251-8. doi: 10.1152/ajpheart.01086.2002. Epub 2003 Mar 20.
The effects of aging on muscle microvascular structure and function may play a key role in performance deficits and impairment of O2 exchange within skeletal muscle of senescent individuals. To determine the effects of aging on capillary geometry, red blood cell (RBC) hemodynamics, and hematocrit in a muscle of mixed fiber type, spinotrapezius muscles from Fischer 344 x Brown Norway hybrid rats aged 6-8 mo [young (Y); body mass 421 +/- 10 g, n = 6] and 26-28 mo [old (O); 561 +/- 12 g, n = 6] were observed by high-resolution transmission light microscopy under resting conditions. The percentage of RBC-perfused capillaries (Y: 78 +/- 3%; O: 75 +/- 2%) and degree of tortuosity and branching (Y: 13 +/- 2%; O: 13 +/- 2%, additional capillary length) were not different in O vs. Y muscles. Lineal density of RBC-perfused capillaries in O was significantly reduced (Y: 30.7 +/- 1.8, O: 22.8 +/- 3.1 capillaries/mm; P < 0.05). However, RBC-perfused capillaries from O rats (n = 78) exhibited increased RBC velocity (VRBC) (Y: 219 +/- 12, O: 310 +/- 14 microm/s; P < 0.05) and RBC flux (FRBC) (Y: 27 +/- 2, O: 41 +/- 2 RBC/s; P < 0.05) vs. Y rats (n = 66). Thus O2 delivery per unit of muscle was not different between groups (Y: 894 +/- 111, O: 887 +/- 118 RBC. s-1. mm muscle-1). Capillary hematocrit was not different in Y vs. O rats (Y: 26 +/- 1%, O: 28 +/- 1%: P > 0.05). These data indicate that in resting spinotrapezius muscle, aging decreases the lineal density of RBC-perfused capillaries while increasing mean VRBC and FRBC within those capillaries. Whereas muscle conductive O2 delivery and capillary hematocrit were unchanged, elevated VRBC reduces capillary RBC transit time and may impair the diffusive transport of O2 from blood to myocyte particularly under exercise conditions.
衰老对肌肉微血管结构和功能的影响可能在衰老个体骨骼肌的性能缺陷和氧气交换受损中起关键作用。为了确定衰老对混合纤维类型肌肉中毛细血管几何形状、红细胞（RBC）血流动力学和血细胞比容的影响，对6 - 8月龄[年轻（Y）；体重421±10克，n = 6]和26 - 28月龄[年老（O）；561±12克，n = 6]的Fischer 344×Brown Norway杂交大鼠的斜方肌在静息条件下通过高分辨率透射光学显微镜进行观察。红细胞灌注毛细血管的百分比（Y：78±3%；O：75±2%）以及曲折度和分支程度（Y：13±2%；O：13±2%，额外的毛细血管长度）在老年组和年轻组肌肉中没有差异。老年组红细胞灌注毛细血管的线性密度显著降低（Y：30.7±1.8，O：22.8±3.1条毛细血管/mm；P < 0.05）。然而，与年轻大鼠（n = 66）相比，老年大鼠（n = 78）的红细胞灌注毛细血管表现出红细胞速度（VRBC）增加（Y：219±12，O：310±14微米/秒；P < 0.05）和红细胞通量（FRBC）增加（Y：27±2，O：41±2个红细胞/秒；P < 0.05）。因此，两组之间每单位肌肉的氧气输送没有差异（Y：894±111，O：887±118个红细胞·秒⁻¹·毫米肌肉⁻¹）。年轻大鼠和老年大鼠的毛细血管血细胞比容没有差异（Y：26±1%，O：28±1%：P > 0.05）。这些数据表明，在静息的斜方肌中，衰老会降低红细胞灌注毛细血管的线性密度，同时增加这些毛细血管内的平均VRBC和FRBC。虽然肌肉传导性氧气输送和毛细血管血细胞比容没有变化，但升高的VRBC会减少毛细血管红细胞通过时间，并且可能会损害氧气从血液到肌细胞的扩散运输，特别是在运动条件下。
