Daniels C R, Eisen V, Slater J D
J Endocrinol. 1987 Mar;112(3):465-72. doi: 10.1677/joe.0.1120465.
A method has been developed which allows estimation of the kinetic parameters of the plasma renin-angiotensinogen reaction from data obtained by autologous renin assays at several plasma dilutions. The quantitative aspects of the renin-angiotensin system were examined in 28 plasma samples from 23 healthy, normotensive pregnant women. They were compared with 20 women who were not pregnant, of whom 12 were taking oral contraceptives and eight were not. In the first 3 months of pregnancy, there was a sharp increase in plasma renin activity and concentration. Plasma angiotensinogen rose steadily throughout pregnancy. The higher concentrations of renin and angiotensinogen would lead to an increase in angiotensin formation with potentially adverse consequences. However, this increase may be reduced by the fall in the affinity between renin and angiotensinogen which is suggested by the present observation that the Michaelis-Menten constant (Km) attained values five to six times higher than those seen in women not taking oral contraceptives. The smaller increases in plasma renin and angiotensinogen induced by oral contraceptives were less effectively compensated by lower affinity. Circumstantial evidence is provided which suggests that the observed high Km values may be due to oestrogen/pregnancy-induced synthesis of an angiotensinogen with a lower affinity for renin.
已开发出一种方法，该方法可根据在几种血浆稀释度下通过自体肾素测定获得的数据来估计血浆肾素 - 血管紧张素原反应的动力学参数。对23名健康、血压正常的孕妇的28份血浆样本中的肾素 - 血管紧张素系统的定量方面进行了检查。将她们与20名未怀孕的女性进行比较，其中12名正在服用口服避孕药，8名未服用。在怀孕的前3个月，血浆肾素活性和浓度急剧增加。血浆血管紧张素原在整个孕期稳步上升。肾素和血管紧张素原浓度的升高会导致血管紧张素形成增加，可能产生不良后果。然而，这种增加可能会因肾素与血管紧张素原之间亲和力的下降而减少，本研究观察到米氏常数（Km）达到的值比未服用口服避孕药的女性高出五到六倍，这表明了这种亲和力的下降。口服避孕药引起的血浆肾素和血管紧张素原较小的增加，通过较低的亲和力得到的补偿效果较差。提供的间接证据表明，观察到的高Km值可能是由于雌激素/怀孕诱导合成了一种对肾素亲和力较低的血管紧张素原。
