Rose J C, Block S M, Flowe K, Morris M, South S, Sundberg D K, Zimmerman C
Am J Physiol. 1987 Feb;252(2 Pt 2):R306-13. doi: 10.1152/ajpregu.1987.252.2.R306.
We compared the cardiovascular and hormonal responses to angiotensin converting enzyme inhibition and hemorrhage of 20% of blood volume in chronically instrumented unanesthetized newborn lambs and adult sheep. Administration of the nonsulfhydryl-containing converting-enzyme inhibitor enalapril reduced mean arterial pressure in the newborn but not in the adult animals. Blood pressure fell in both age groups after hemorrhage, and the hemorrhage-induced fall in blood pressure, integrated over the period of hypovolemia, was more pronounced when converting-enzyme inhibition was present in the lambs. This was not observed in the adults. Cardiac output fell following hemorrhage in both age groups, and the fall was greater when enalapril was present in the lambs, but this was not the case in the adults. Hemorrhage increased plasma renin activity in both groups, and enalapril augmented this increase. Plasma concentrations of vasopressin and catecholamines increased following hemorrhage within and between groups. Taken together these data suggest that the renin-angiotensin system plays a more important role in the maintenance of cardiovascular homeostasis in newborn lambs than it does in adult sheep, and catecholamine and vasopressin responses to volume loss can occur in the presence of blockade of the renin-angiotensin system.
我们比较了长期植入仪器的未麻醉新生羔羊和成年绵羊对血管紧张素转换酶抑制及失血量达血容量20%的出血情况的心血管和激素反应。给予不含巯基的血管紧张素转换酶抑制剂依那普利可降低新生羔羊的平均动脉压，但对成年动物无此作用。两个年龄组在出血后血压均下降，在低血容量期间，当羔羊存在血管紧张素转换酶抑制时，出血诱导的血压下降更为明显。成年动物未观察到这种情况。两个年龄组在出血后心输出量均下降，当羔羊使用依那普利时下降幅度更大，但成年动物并非如此。出血使两组血浆肾素活性均增加，依那普利增强了这种增加。出血后两组内及组间血管加压素和儿茶酚胺的血浆浓度均升高。综合这些数据表明，肾素-血管紧张素系统在维持新生羔羊心血管稳态中比在成年绵羊中发挥更重要的作用，并且在肾素-血管紧张素系统被阻断的情况下，对容量丢失的儿茶酚胺和血管加压素反应仍可发生。
