Souhrada J F, Dickey D W
J Appl Physiol Respir Environ Exerc Physiol. 1977 Mar;42(3):438-43. doi: 10.1152/jappl.1977.42.3.438.
The present study demonstrates the reactivity of isolated main pulmonary artery (MPA) from guinea pigs and rats to two vasoactive drugs, norepinephrine (NE) and histamine (H), in substrate-rich and substrate-free medium, under both aerobic (PO2 = 95 +/- 0.5 Torr) and hypoxic conditions (PO2 = 30 +/- 1 Torr). The sensitivity of MPA from guinea pigs to NE and H during aerobic conditions is not significantly affected by the absence of substrate in the experimental medium. Furthermore, it is demonstrated that in the substrate-rich experimental medium (5.5 mM glucose), the reactivity of MPA from guinea pigs to NE and H is not significantly affected by acute hypoxia as compared with the response of MPA during aerobic conditions. These experiments contrast with data obtained when substrate is absent from the experimental medium. The dose-response curves of MPA from guinea pigs to NE and H under this condition were significantly blunted during hypoxia. Following the completion of the dose-response curves during aerobic conditions, with both NE and H, spontaneous mechanical activities were seen in the guinea pig MPA. On the other hand, it was demonstrated that during aerobic and hypoxic conditions MPA's isolated from rats exhibit no physiological response to histamine even when administered in the dose required to produce the maximal response in MPA isolated from guinea pigs. The sensitivity of MPA from rats to NE during aerobic conditions is not significantly affected by the absence of substrate in the experimental medium. However, when the preparation was exposed to hypoxia, the presence of substrate failed to maintain the reactivity of MPA to norepinephrine. In addition, MPA isolated from rats demonstrated a smaller contractile response to NE than those from guinea pigs. Furthermore, no spontaneous mechanical activities were observed after norepinephrine or histamine administration. The present study, in addition to pointing out species differences, shows the important role of exogenous substrate in maintaining the reactivity of pulmonary vascular smooth muscle during hypoxia.
本研究证明了从豚鼠和大鼠分离出的主肺动脉（MPA）在富底物和无底物培养基中，于有氧（PO2 = 95 ± 0.5 Torr）和低氧条件（PO2 = 30 ± 1 Torr）下对两种血管活性药物去甲肾上腺素（NE）和组胺（H）的反应性。在有氧条件下，实验培养基中缺乏底物对豚鼠MPA对NE和H的敏感性没有显著影响。此外，还证明了在富底物的实验培养基（5.5 mM葡萄糖）中，与有氧条件下MPA的反应相比，豚鼠MPA对NE和H的反应性不受急性低氧的显著影响。这些实验与实验培养基中无底物时获得的数据形成对比。在此条件下，豚鼠MPA对NE和H的剂量反应曲线在低氧时明显变钝。在有氧条件下完成NE和H的剂量反应曲线后，豚鼠MPA中出现了自发机械活动。另一方面，证明了在有氧和低氧条件下，从大鼠分离出的MPA即使给予在从豚鼠分离出的MPA中产生最大反应所需的剂量，对组胺也无生理反应。在有氧条件下，实验培养基中缺乏底物对大鼠MPA对NE的敏感性没有显著影响。然而，当制剂暴露于低氧时，底物的存在未能维持MPA对去甲肾上腺素的反应性。此外，从大鼠分离出的MPA对NE的收缩反应比从豚鼠分离出的MPA小。此外，给予去甲肾上腺素或组胺后未观察到自发机械活动。本研究除了指出种属差异外，还表明了外源性底物在低氧期间维持肺血管平滑肌反应性中的重要作用。
