Anke J, Van Eekelen M, Phillips M I
Department of Physiology, College of Medicine, University of Florida, Gainesville 32610.
Am J Physiol. 1988 Sep;255(3 Pt 2):R500-6. doi: 10.1152/ajpregu.1988.255.3.R500.
Angiotensin II (ANG II) was infused intravenously within an apparent physiological dose range of 10-200 ng.kg-1.min-1 to induce a drinking response in rats. To determine the plasma ANG II level at the moment of drinking, blood samples were collected from the femoral artery at the onset of the drinking response. Control blood samples were obtained in a similar way before infusion. The lowest dose of ANG II did not evoke drinking. Variable water intake in response to 25, 50, and 75 ng ANG II.kg-1.min-1 after a relatively long latency to drink (40-65 min) was observed. All animals showed a drinking response when 100 ng ANG II.kg-1.min-1 or higher doses of ANG II were infused. The latencies to drink were inversely correlated to the dose of ANG II and were as short as 8 min with 200 ng ANG II.kg-1.min-1. Measurement of ANG II in the plasma of drinking rats showed that all concentrations were similar with an average of 458 +/- 58.1 pg/ml. This dipsogenic plasma ANG II level is equivalent to plasma ANG II after 48 h of dehydration. The results show that drinking in response to exogenous intravenous ANG II requires a threshold level to be reached that is equivalent to levels produced by the endogenous renin-angiotensin system when dehydration is prolonged. This suggests that intravenous ANG II is not involved in moment-to-moment fluid homeostasis but operates only when dehydration is severe.
以10 - 200 ng·kg⁻¹·min⁻¹的表观生理剂量范围静脉输注血管紧张素II（ANG II）以诱导大鼠产生饮水反应。为了确定饮水时的血浆ANG II水平，在饮水反应开始时从股动脉采集血样。在输注前以类似方式获取对照血样。最低剂量的ANG II未引起饮水。观察到在相对较长的饮水潜伏期（40 - 65分钟）后，对25、50和75 ng ANG II·kg⁻¹·min⁻¹有不同的饮水量。当输注100 ng ANG II·kg⁻¹·min⁻¹或更高剂量的ANG II时，所有动物均表现出饮水反应。饮水潜伏期与ANG II剂量呈负相关，在200 ng ANG II·kg⁻¹·min⁻¹时短至8分钟。对饮水大鼠血浆中的ANG II进行测量显示，所有浓度相似，平均为458±58.1 pg/ml。这种致渴性血浆ANG II水平相当于脱水48小时后的血浆ANG II水平。结果表明，对外源性静脉注射ANG II的饮水反应需要达到一个阈值水平，该水平相当于长时间脱水时内源性肾素 - 血管紧张素系统产生的水平。这表明静脉注射ANG II不参与即时的液体稳态，仅在严重脱水时起作用。
