Krieger J E, Roman R J, Cowley A W
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
Am J Physiol. 1989 Nov;257(5 Pt 2):H1402-12. doi: 10.1152/ajpheart.1989.257.5.H1402.
The sequential effects of an increased daily NaCl intake on hemodynamics, fluid electrolyte balances, and hormonal responses were evaluated in dogs (n = 7) with fixed circulating levels of angiotensin II (ANG II). During the control period, ANG II was infused at 3 ng.kg-1.min-1 while dogs were maintained on an 8 meq NaCl/day diet. Water intake was fixed at 700 ml/day. Continuously recorded (24 h/day) changes of total body weight (TBW) were used as an index of total body water. Cardiac stroke volume and arterial pressure were recorded, and each beat was digitized to provide hourly and 24-h average cardiac output (CO), mean arterial pressure (MAP), and total peripheral resistance (TPR). After three stable control days, daily salt intake was increased to 120 meq for 7 days. TBW increased gradually to 448 +/- 111 g (2.9%, P less than 0.05) above control by day 3. An 11% expansion of blood volume (P less than 0.05) was found (51CR-labeled red blood cells) on day 2 of high NaCl. CO rose 12% and MAP 20% (P less than 0.05) in parallel with TBW by day 4. By day 7, CO remained only 5% elevated, whereas MAP had stabilized at 20% above control levels. TPR remained significantly elevated from days 3 through 7. A positive Na balance averaging 91 +/- 8 meq (P less than 0.05) occurred on day 1. Plasma Na concentration was increased 2-3 meq/l above control throughout the period of high-salt intake. Plasma renin activity and aldosterone levels decreased to nearly undetectable levels, vasopressin rose slightly, and atrial natriuretic peptide levels increased significantly. Dogs maintained at 8 meq/day NaCl during the same infusion of ANG II showed no changes in MAP, CO, TPR, or TBW. In summary, the salt-induced hypertension was consistently related to small but significant fluid retention, blood volume expansion, elevations of cardiac output, and a gradual increase in TPR.
在循环中血管紧张素II（ANG II）水平固定的犬类（n = 7）中，评估了每日氯化钠摄入量增加对血流动力学、液体电解质平衡和激素反应的连续影响。在对照期，以3 ng·kg-1·min-1的速率输注ANG II，同时犬类维持在每日8 meq氯化钠的饮食。水摄入量固定为每日700 ml。连续记录（每天24小时）的总体重（TBW）变化用作总体水的指标。记录心搏量和动脉压，并且将每个搏动数字化以提供每小时和24小时的平均心输出量（CO）、平均动脉压（MAP）和总外周阻力（TPR）。在三个稳定的对照日后，每日盐摄入量增加到120 meq，持续7天。到第3天，TBW逐渐增加到比对照高448±111 g（2.9%，P<0.05）。在高氯化钠摄入的第2天，发现血容量增加了11%（P<0.05）（51Cr标记的红细胞）。到第4天，CO升高了12%，MAP升高了20%（P<0.05），与TBW平行。到第7天，CO仅升高5%，而MAP稳定在比对照水平高20%。从第3天到第7天，TPR仍然显著升高。第1天出现平均为91±8 meq的正钠平衡（P<0.05）。在高盐摄入期间，血浆钠浓度比对照升高2 - 3 meq/l。血浆肾素活性和醛固酮水平降至几乎无法检测的水平，血管加压素略有升高，心房利钠肽水平显著增加。在相同的ANG II输注期间维持在每日8 meq氯化钠的犬类，其MAP、CO、TPR或TBW没有变化。总之，盐诱导的高血压始终与少量但显著的液体潴留、血容量扩张、心输出量升高以及TPR逐渐增加有关。
