Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus, Denmark.
Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus, Denmark; Aarhus Institute of Advanced Studies, 8000 Aarhus C, Denmark.
Comp Biochem Physiol A Mol Integr Physiol. 2021 Feb;252:110839. doi: 10.1016/j.cbpa.2020.110839. Epub 2020 Nov 7.
Angiotensin II (ANG II) is part of the renin-angiotensin system (RAS) in vertebrates and exert vasoconstriction in all species studied. The present study examines the vasopressor effect of ANG II in the ball python (Python regius), and examines whether ANG II exert its effect through direct angiotensin receptors or through an activation of α-adrenergic receptors. The studies were conducted in snakes with chronic arterial catheters that had recovered from anesthesia. In addition to demonstrating a clear and pronounced dose-dependent rise in arterial blood pressure upon repeated injections of boluses with ANG II (0.001-1 μg/kg), we demonstrate that the pressor response persisted following α-adrenergic blockade using the α-adrenergic antagonist phentolamine (2.5 mg/kg). Unfortunately, it proved impossible to block the ANG receptors using losartan (1, 3 or even 10 mg/kg). The pressor response to ANG II was associated with a significant rise in heart rate at the higher dosages, pointing to a resetting of the barostatic mechanism for heart rate regulation. The responses were similar in fasting and digesting pythons despite the expected rise in baseline values for blood pressure and heart rate of the digesting snakes.
血管紧张素 II（ANG II）是脊椎动物肾素-血管紧张素系统（RAS）的一部分，在所有研究过的物种中都具有血管收缩作用。本研究检查了 ANG II 在球蟒（Python regius）中的升压作用，并检查了 ANG II 是否通过直接血管紧张素受体或通过激活α-肾上腺素能受体发挥作用。这些研究是在从麻醉中恢复过来的具有慢性动脉导管的蛇中进行的。除了证明在反复注射 ANG II（0.001-1μg/kg）的情况下，动脉血压明显且呈剂量依赖性升高外，我们还证明了使用α-肾上腺素能拮抗剂苯肾上腺素（2.5mg/kg）阻断α-肾上腺素能受体后，升压反应仍然存在。不幸的是，使用氯沙坦（1、3 甚至 10mg/kg）阻断 ANG 受体证明是不可能的。ANG II 的升压反应与较高剂量下心率的显著升高有关，这表明心率调节的压力平衡机制被重置。尽管消化蛇的血压和心率的基线值预计会升高，但禁食和消化的蟒蛇的反应相似。
