Voelkel N F, Morris K G, McMurtry I F, Reeves J T
J Appl Physiol Respir Environ Exerc Physiol. 1980 Sep;49(3):450-5. doi: 10.1152/jappl.1980.49.3.450.
Isolated lungs from high-altitude rats compared with those from low-altitude rats have blunted hypoxic pressor responses. Because calcium is essential for the hypoxic pressor response and has been shown to be altered in the pulmonary arterial smooth muscle during high-altitude exposure, we wondered whether altered calcium metabolism might account for the blunted response. We attempted to unmask differences between high- and low-altitude rat lungs by altering extracellular calcium. The addition of calcium to the blood perfusate augmented the hypoxic pressure response of high-altitude lungs and depressed that of low-altitude lungs. Calcium addition did not affect pressor responses to angiotensin II, but slowed vasodilation after both angiotensin injection and removal of the hypoxic stimulus. The maximal KCl-induced contraction was blunted in rings of main pulmonary artery from high-altitude rats, but augmented in their aortic rings. Submaximally constricted (40 mM KCl) pulmonary arteries from low- but not high-altitude rats further constricted with calcium addition. Aortic rings exhibited an inverse behavior. Thus, calcium addition augmented the blunted vasopressor response in high-altitude rats lungs, possibly by an effect on lung arteries. The aorta and main pulmonary artery differ in calcium handling.
与低海拔大鼠的离体肺相比，高海拔大鼠的离体肺对低氧的升压反应减弱。由于钙对于低氧升压反应至关重要，并且在高海拔暴露期间已显示肺动脉平滑肌中的钙会发生变化，我们想知道钙代谢的改变是否可能是导致反应减弱的原因。我们试图通过改变细胞外钙来揭示高海拔和低海拔大鼠肺之间的差异。向血液灌流液中添加钙增强了高海拔肺的低氧压力反应，并减弱了低海拔肺的低氧压力反应。添加钙并不影响对血管紧张素II的升压反应，但在注射血管紧张素和去除低氧刺激后均减缓了血管舒张。高海拔大鼠主肺动脉环中最大氯化钾诱导的收缩减弱，但其主动脉环中的收缩增强。低海拔而非高海拔大鼠的亚最大收缩（40 mM氯化钾）肺动脉在添加钙后进一步收缩。主动脉环表现出相反的行为。因此，添加钙可能通过对肺血管的作用增强了高海拔大鼠肺中减弱的血管升压反应。主动脉和主肺动脉在钙处理方面存在差异。
