Analysis of intracellular mechanisms and related factors regarding spinal protection by remote preoonditioning

用戊巴比妥麻醉家兔，测定颅窗预备术中脑脊膜血管直径和脊髓局部组织氧压（PtO2）。我们根据以下方案调查实验。1)我们研究了主动脉夹持和去主动脉夹持作为一种远程预处理干预对脑血管直径的影响。虽然肾下主动脉交叉夹紧不影响心梗血管直径，但释放20分钟的主动脉交叉夹紧引起心梗小动脉先扩张后收缩。明显的收缩持续了至少60分钟。为了阐明体液因子的远程预适应机制，我们研究了血管紧张素II型受体阻滞剂、rho激酶抑制剂或自由基清除剂是否会影响主动脉交叉夹持和脑血管释放后的反应。这三种药物均能显著减轻心肌小动脉的收缩。因此，血管紧张素II、rho激酶和自由基可能是与脊髓保护远程调节相关的体液因子的候选者。2)通过直接测量脊髓组织氧分压，评价远程预处理对脊髓缺血性损伤的预防作用。预适应干预组在主动脉交叉夹持后20 min和主动脉解夹持后0.2 min的PtO2明显降低。与对照组相比，前肢和后肢远程预处理保护了PtO2的降低。因此，这种干预对PtO2的影响可能与短暂性上肢和下肢缺血远程预适应诱导的脊髓保护机制有关。

Pentobarbital anesthetized rabbits were prepared for measurement of cerebral pial vessel diameter in a cranial window preparation or spinal cord partial tissue oxygen pressure (PtO2). We investigated the experiments according to following protocols.1) We studied the effect of aortic clamping and declamping as a remote preconditioning intervention on cerebral pial vessel diameter. Although infrarenal aortic cross-clamping did not affect pial vessel diameter, release of a 20-min aortic cross-clamp caused pial arterioles to dilate and then constrict. A significant constriction persisted for at least 60 min. To clarify the mechanism of remote preconditioning regarding humoral factor, we examined whether angiotensin II typel receptor blocker, Rho-kinase inhibitor, or free radical scavenger, would affect the respose observed after aortic cross-clamping and release on cerebral vessels. All three drugs significantly attenuated the constriction of pial arterioles. Thus angiotensin II, Rho-kinase, and free radical could be possible to be candidates for humoral factors related to remote conditioning on spinal protection.2) We measured directly the tissue oxygen partial pressure of the spinal cord to assess the efficacy of remote preconditioning in preventing apinal cord ischemic injury in an experimental model. PtO2 were significantly lower in the preconditioning intervention group at 20 min after aortic cross-clamping and 0, 2 min after aortic unclamping. Remote preconditioning performed in fore and hind legs protected the decrease of PtO2 compared with control group. Thus, the effect on PtO2 by such intervention may relate to the mechanism of spinal protection induced by remote preconditioning by transient upper and lower limbs ischemia.