Yung W H, Chiu K W
Gen Comp Endocrinol. 1985 Nov;60(2):259-65. doi: 10.1016/0016-6480(85)90322-3.
Vasopressor action is a phylogenetically old function of angiotensin (ANG) II. The action can be ascribed to both direct activation of vascular ANG II receptors and through catecholamine release. In the Rat snake, Ptyas korros, the possible presence of common adrenergic-ANG receptors and their involvement in this action have been proposed. In order to elucidate the vasopressor mechanism of ANG II in the snake, and to test the presence of common adrenergic-ANG receptors, the contractile response of isolated snake dorsal aorta to [Val5]ANG II and norepinephrine (NE) was studied using the cobra, Naja naja and the Rat snake, Ptyas korros. Both ANG II (3 X 10(-11) to 10(-6) M) and NE (10(-8) to 10(-5) M) produced a dose-dependent increase in tension in the aortic strips of Naja, which were more sensitive to ANG II. Phenotolamine, an alpha-adrenergic antagonist, competitively inhibited NE without altering the response to ANG II. [Sar1, Ala8]ANG II inhibited ANG II but did not affect the response to NE. A similar dose-dependent increase in tension in the aortic strips of Ptyas was seen with NE (10(-8) to 10(-5) M) but these strips did not respond to ANG II. These results suggest that functionally separate receptors for ANG II and NE exist in the dorsal aorta of the cobra and that local liberation of catecholamines from the adrenergic nerve terminals do not play a role in the expression of ANG II action. There also exist differences in the nature of ANG II action/receptors among different species of snakes and different vascular beds in the same species.
血管收缩作用是血管紧张素（ANG）II在系统发育上的古老功能。该作用既可以归因于血管ANG II受体的直接激活，也可以通过儿茶酚胺释放来实现。在锦蛇（Ptyas korros）中，有人提出可能存在共同的肾上腺素能-ANG受体及其在该作用中的参与。为了阐明蛇体内ANG II的血管收缩机制，并测试共同的肾上腺素能-ANG受体的存在，使用眼镜蛇（Naja naja）和锦蛇（Ptyas korros）研究了离体蛇背主动脉对[Val5]ANG II和去甲肾上腺素（NE）的收缩反应。ANG II（3×10⁻¹¹至10⁻⁶ M）和NE（10⁻⁸至10⁻⁵ M）均可使眼镜蛇主动脉条带的张力呈剂量依赖性增加，且对ANG II更敏感。α-肾上腺素能拮抗剂酚妥拉明竞争性抑制NE，但不改变对ANG II的反应。[Sar1，Ala8]ANG II抑制ANG II，但不影响对NE的反应。锦蛇主动脉条带对NE（10⁻⁸至10⁻⁵ M）也有类似的剂量依赖性张力增加，但这些条带对ANG II无反应。这些结果表明，眼镜蛇背主动脉中存在功能上独立的ANG II和NE受体，并且来自肾上腺素能神经末梢的儿茶酚胺局部释放对ANG II作用的表达不起作用。不同种类的蛇以及同一物种的不同血管床之间，ANG II作用/受体的性质也存在差异。
