Ebeigbe A B, Pickard J D, Jennett S
Q J Exp Physiol Cogn Med Sci. 1980 Oct;65(4):273-92. doi: 10.1113/expphysiol.1980.sp002517.
The rapidity and extent of hypoxic relaxation of vascular smooth muscle (VSM) from different systemic vessels is relevant to the study of mechanisms of vasodilation in different vascular beds. Variations between sites may also assist understanding of the link between oxygen tension and mechanical activity, which has been shown not to be a simple deprivation of aerobic processes. Strips of rat portal vein (RPV), rabbit ear artery (REA) and rabbit common carotid artery (RCC) were studied under isotonic conditions, contracted by 10(-6) noradrenaline (NA). Reduction of Po2 to less than 3KPa during NA constraction led to relaxation which was rapid and 90% complete in RPV, rapid and 60% in REA: the relaxation began when tissue Po2 was decreasing and was not lower than 5.5 K Pa. RCC responded slowly and only some strips relaxed. The rapidity and magnitude of relaxation for each type of vessel was comparable to that produced by removal of external calcium. Also for any one type of VSM the response to NA was abolished or diminished to a similar extent by preliminary exposure to hypoxia, or by preliminary removal of calcium. Preliminary hypoxia diminished 50 mmol.1(-1) K+ contractions as much as it diminished NA contractions. Preliminary 1-2 hour exposure to hyperoxia diminished the subsequent relaxant effect of hypoxia. Inhibition of glycolysis (iodoacetic acid) had no effect on normoxic NA contraction or on hypoxic relaxation, but prevented or diminished the subsequent recovery on reoxygenation. Low oxygen tension appears to act in VSM as though it interferes with net influx or utilisation of external calcium.
不同体循环血管的血管平滑肌（VSM）缺氧性舒张的速度和程度与不同血管床血管舒张机制的研究相关。不同部位之间的差异也有助于理解氧张力与机械活动之间的联系，已表明这种联系并非简单的有氧代谢过程缺失。在等张条件下研究了大鼠门静脉（RPV）、兔耳动脉（REA）和兔颈总动脉（RCC）的肌条，用10⁻⁶去甲肾上腺素（NA）使其收缩。在NA收缩期间将氧分压（Po₂）降至低于3kPa会导致舒张，在RPV中舒张迅速且90%完成，在REA中迅速且60%完成：舒张在组织Po₂下降时开始且不低于5.5kPa。RCC反应缓慢，只有一些肌条舒张。每种血管的舒张速度和幅度与去除细胞外钙所产生的情况相当。同样，对于任何一种类型的VSM，预先暴露于缺氧或预先去除钙后，对NA的反应会被消除或减弱到相似程度。预先缺氧使50mmol·L⁻¹ K⁺收缩减弱的程度与使NA收缩减弱的程度相同。预先1 - 2小时暴露于高氧会减弱随后缺氧的舒张作用。抑制糖酵解（碘乙酸）对常氧下的NA收缩或缺氧性舒张无影响，但会阻止或减弱复氧后的后续恢复。低氧张力在VSM中的作用似乎就好像它干扰了细胞外钙的净内流或利用。
