Dane D Merrill, Hsia Connie C W, Wu Eugene Y, Hogg Richard T, Hogg Deborah C, Estrera Aaron S, Johnson Robert L
Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390-9034, USA.
J Appl Physiol (1985). 2006 Jul;101(1):289-97. doi: 10.1152/japplphysiol.01600.2005. Epub 2006 Apr 6.
The spleen acts as an erythrocyte reservoir in highly aerobic species such as the dog and horse. Sympathetic-mediated splenic contraction during exercise reversibly enhances convective O2 transport by increasing hematocrit, blood volume, and O2-carrying capacity. Based on theoretical interactions between erythrocytes and capillary membrane (Hsia CCW, Johnson RL Jr, and Shah D. J Appl Physiol 86: 1460-1467, 1999) and experimental findings in horses of a postsplenectomy reduction in peripheral O2-diffusing capacity (Wagner PD, Erickson BK, Kubo K, Hiraga A, Kai M, Yamaya Y, Richardson R, and Seaman J. Equine Vet J 18, Suppl: 82-89, 1995), we hypothesized that splenic contraction also augments diffusive O2 transport in the lung. Therefore, we have measured lung diffusing capacity (DL(CO)) and its components during exercise by a rebreathing technique in six adult foxhounds before and after splenectomy. Splenectomy eliminated exercise-induced polycythemia, associated with a 30% reduction in maximal O2 uptake. At any given pulmonary blood flow, DL(CO) was significantly lower after splenectomy owing to a lower membrane diffusing capacity, whereas pulmonary capillary blood volume changed variably; microvascular recruitment, indicated by the slope of the increase in DL(CO) with respect to pulmonary blood flow, was also reduced. We conclude that splenic contraction enhances both convective and diffusive O2 transport and provides another compensatory mechanism for maintaining alveolar O2 transport in the presence of restrictive lung disease or ambient hypoxia.
在诸如犬和马等高氧物种中，脾脏充当红细胞储存库。运动期间交感神经介导的脾脏收缩通过增加血细胞比容、血容量和携氧能力，可逆地增强对流性氧气运输。基于红细胞与毛细血管膜之间的理论相互作用（夏长赐、小约翰逊·R·L、沙阿·D。《应用生理学杂志》86：1460 - 1467，1999年）以及马匹脾切除术后外周氧气扩散能力降低的实验结果（瓦格纳·P·D、埃里克森·B·K、久保·K、平贺·A、凯·M、山屋·Y、理查森·R、西曼·J。《马兽医杂志》18增刊：82 - 89，1995年），我们推测脾脏收缩也会增强肺内的扩散性氧气运输。因此，我们采用重复呼吸技术，在六只成年猎狐犬脾切除术前和术后运动期间测量了肺扩散容量（DL(CO)）及其组成部分。脾切除消除了运动诱导的红细胞增多症，同时最大摄氧量降低了30%。在任何给定的肺血流量下，脾切除术后DL(CO)显著降低，原因是膜扩散能力降低，而肺毛细血管血容量变化不定；由DL(CO)相对于肺血流量增加的斜率表示的微血管募集也减少了。我们得出结论，脾脏收缩增强了对流性和扩散性氧气运输，并为在存在限制性肺病或环境性缺氧的情况下维持肺泡氧气运输提供了另一种代偿机制。
