Stephens G A
Gen Comp Endocrinol. 1984 May;54(2):175-80. doi: 10.1016/0016-6480(84)90170-9.
In order to better understand the vascular effects of angiotensin II (AII) in lower vertebrates, the contractile responses of aortic strips from the freshwater turtle Pseudemys scripta elegans were studied. Circumferential strips from the left aortic arch were suspended in a tissue bath in 25 degrees C reptilian Ringer's solution at pH 7.5. Both [Asn1,Val5] AII (10(-9)-10(-5) M) and norepinephrine (NE) (10(-8)-10(-4) M) produced dose-dependent contractions. The threshold dosage for AII was between 10(-9) and 10(-8) M and for NE between 10(-8) and 10(-7) M. Pretreatment with [Sar1,Ile8] AII (10(-6) M) significantly attenuated the response to [Asn1,Val5] AII at 10(-5) M and totally blocked the response at lower AII concentration (P less than 0.01 in each case). The response to AII was unaffected by phentolamine (10(-6) M). Phentolamine abolished the response to NE at concentrations of 10(-6) M or less (P less than 0.01) and attenuated the response by 48% at 10(-5) M (P less than 0.05) and 43% at 10(-4) M (P less than 0.05) NE. The response to NE was unaffected by [Sar1,Ile8] AII. The results demonstrate that [Asn1,Val5] AII has a direct contractile effect on turtle vasculature and that two functionally distinct vascular receptor populations for AII and NE are present in the turtle. Since phentolamine did not affect the responses to AII, it also appears that angiotensin-evoked norepinephrine release from the sympathetic nerve terminals in the vessel is not involved in the angiotensin-induced contractions in this preparation.
为了更好地理解血管紧张素II（AII）对低等脊椎动物血管的影响，研究了淡水龟丽锦龟主动脉条的收缩反应。取自左主动脉弓的环行条带被悬挂于25摄氏度、pH值为7.5的爬行动物林格氏液的组织浴中。[天冬酰胺1，缬氨酸5]AII（10^(-9)-10^(-5)M）和去甲肾上腺素（NE）（10^(-8)-10^(-4)M）均产生剂量依赖性收缩。AII的阈剂量在10^(-9)和10^(-8)M之间，NE的阈剂量在10^(-8)和10^(-7)M之间。用[肌氨酸1，异亮氨酸8]AII（10^(-6)M）预处理可显著减弱10^(-5)M[天冬酰胺1，缬氨酸5]AII的反应，并在较低AII浓度时完全阻断反应（每种情况P均小于0.01）。酚妥拉明（10^(-6)M）不影响对AII的反应。酚妥拉明在10^(-6)M或更低浓度时可消除对NE的反应（P小于0.01），在10^(-5)M时使反应减弱48%（P小于0.05），在10^(-4)M NE时使反应减弱43%（P小于0.05）。[肌氨酸1，异亮氨酸8]AII不影响对NE的反应。结果表明，[天冬酰胺1，缬氨酸5]AII对龟血管有直接收缩作用，且龟体内存在两种功能不同的AII和NE血管受体群体。由于酚妥拉明不影响对AII的反应，血管紧张素引起的交感神经末梢去甲肾上腺素释放似乎也不参与本实验中血管紧张素诱导的收缩。
