Kohzuki H, Enoki Y, Matsumura K, Sakata S, Shimizu S
Department of Physiology, Nara Medical University, Japan.
J Appl Physiol (1985). 1996 Mar;80(3):832-8. doi: 10.1152/jappl.1996.80.3.832.
To evaluate the influence of a high-O2 affinity of the erythrocyte and of flow rate on muscle's ability to extract O2 and develop force, we perfused dog gastrocnemius contracting isometrically at 4 Hz with normal-O2-affinity perfusate or high-O2-affinity perfusate at high and moderate flows (200 and 100 ml . min-1 . 100g-1, respectively). High-O2-affinity perfusate was prepared by incubating human citrate-phosphate-dextrose-stored erythrocytes with buffered saline containing cyanate (4 degrees C, 18 h) and normal-affinity perfusate by storing 2,3-diphosphoglycerate-rejuvenated erythrocytes in the same solution without cyanate. PO2 when blood is half oxygenated was 30.6 Torr for normal perfusate and 18.1 Torr for high-affinity perfusate. During 4-Hz stimulation, the tension developed by the muscle increased incrementally (positive staircase) to reach a peak value after 1.2-1.6 min for the normal perfusate and 0.6-0.7 min for the high-affinity perfusate (P < 0.05). The rate of decline during the early fatigue (measured from the onset of tension decline to 3 min) with high-affinity perfusate was significantly faster than it was with normal perfusate (P < 0.05). These findings suggest that both the staircase effect and the early fatigue are related to O2 availability, which is restricted when erythrocytes have a high O2 affinity. The peak O2 uptake values measured at 3 and 5 min were significantly lower (by 14-24%) with high-affinity perfusate than with normal perfusate at a given level of O2 delivery (arterial O2 content x flow) (P < 0.05). PO2 of venous effluent was proportionally related to peak O2 uptake. The present results indicate that neither blood flow nor O2 delivery is the sole determinant of the muscle's ability to extract O2.
为评估红细胞的高氧亲和力和流速对肌肉摄取氧气及产生力量能力的影响，我们以4Hz频率对等长收缩的犬腓肠肌进行灌注，分别使用正常氧亲和力灌注液或高氧亲和力灌注液，在高流量和中等流量（分别为200和100ml·min⁻¹·100g⁻¹）下进行。高氧亲和力灌注液通过将人柠檬酸 - 磷酸盐 - 葡萄糖保存的红细胞与含氰酸盐的缓冲盐水（4℃，18小时）孵育制备，正常亲和力灌注液则通过将2,3 - 二磷酸甘油酸复壮的红细胞保存在不含氰酸盐的相同溶液中制备。正常灌注液血液半氧合时的PO₂为30.6托，高亲和力灌注液为18.1托。在4Hz刺激期间，正常灌注液时肌肉产生的张力在1.2 - 1.6分钟后逐渐增加（正阶梯现象）达到峰值，高亲和力灌注液时在0.6 - 0.7分钟后达到峰值（P < 0.05）。早期疲劳期间（从张力下降开始至3分钟测量），高亲和力灌注液时的张力下降速率明显快于正常灌注液（P < 0.05）。这些发现表明，阶梯效应和早期疲劳均与氧气供应有关，当红细胞具有高氧亲和力时，氧气供应受限。在给定的氧气输送水平（动脉血氧含量×流量）下，3分钟和5分钟时测量的峰值摄氧量，高亲和力灌注液显著低于正常灌注液（低14 - 24%）（P < 0.05）。静脉流出液的PO₂与峰值摄氧量成比例相关。目前的结果表明，血流量和氧气输送都不是肌肉摄取氧气能力的唯一决定因素。
