The physiologic baroreceptor activity and fetal plasma amino acids under chronic hypoxemia in fetal lamb.

目的探讨慢性低氧血症对胎羊压力感受性反射（BR）和胎羊血浆氨基酸浓度的影响。（方法）对9只妊娠100 ~ 127天的胎羊进行BR实验和胎羊血浆氨基酸浓度测定。母体气管内持续输注氮气诱导胎儿缺氧。为分析胎仔BR活性，在正常或低氧组的第1、5、10、15天连续行为周期内注射去甲肾上腺素5 ~ 7.5 μg。在胎羊中，测量平均动脉血压（MAP）和FHR，分为活动状态（AS）和睡眠状态（SS），其通过反应性或胎儿呼吸运动来回顾性地确定。计算注射去甲肾上腺素后最大胎心率下降与最大平均动脉压升高的比值（ΔFHR/ΔMAP）， ...更多信息 显示胎儿BR活性。将行为状态分为睡眠状态（SS）和活动状态（AS），并分为低氧血症组（H组）和常氧血症组（N组）。随后，我们对胎龄（GA）与ΔFHR/ΔMAP的关系进行了一元回归分析。（结果与结论）GA的增加导致两种状态下及两组BR的降低，N组：Y=-0.042X+8.306（p=0.043）（AS）Y=-0.046X+8.57（p=0.0007）（SS）H组：Y=-0.041X+7.63（p=0.017）（AS），Y=-0.063X+10.0（p=0.021）（SS）表明，在慢性低氧条件下，胎羊BR随GA增加而降低的趋势比对照组更为显著。胎儿产生蛋白质和能量所需的氨基酸，与其他氨基酸相比，在慢性低氧血症中表现出明显的下降趋势。胎儿血浆中的糖原生成氨基酸的浓度，显着降低母亲饥饿，并没有显示出下降的趋势，在慢性低氧血症。少

(Objective)The purpose of this study was to investigate the variation of baroreflex (BR) and fetal plasma concentrations of amino acids under the chronic hypoxemia in the fetal lamb.(Methods)We conducted BR experiments and measurement of fetal plasma concentrations of amino acids simultaneously on nine chronically instrumented fetal lambs (100〜127 days of gestation). Continuous infusion of nitrogen into maternal trachea induced the fetal hypoxic condition. To analysis fetal BR activity, injections of 5 - 7.5 μg of norepinephrine were given during consecutive behavioral cycle on the 1, 5, 10, 15th day in normoxemic or hypoxemic groups. In fetal lambs, mean arterial blood pressure (MAP) and FHR was measured dividing into active states (AS) and sleep states (SS) which were determined retrospectively by reactivity or fetal breathing movements. The ratio of maximal FHR decrease to maximal MAP increase (ΔFHR/ΔMAP) response to the norepinephrine injections was calculated to quantitatively rep … More resent fetal BR activity. Furthermore, we classified behavior state into sleep state (SS) and active state (AS), and classified into the hypoxemia group (H group) and the normoxemia group (N group). Thereafter, we did single regression analysis about the relation between the gestational age (GA) and ΔFHR/ΔMAP.(Results and Conclusions)The increasing in GA induced decreasing of BR in both states and in both groups.N group : Y=-0.042X+8.306(p=0.043)(AS) Y=-0.046X+8.57(p=0.0007)(SS)H group : Y=-0.041X+7.63(p=0.017)(AS), Y=-0.063X+10.0(p=0.021)(SS)These date suggested that under chronic hypoxemia the decreasing of BR with increasing in GA was more significant than that of the controls in fetal lamb.Fetal plasma concentrations of the branched chain amino acids, that were needed to produce protein and energy in fetuses, showed a decrease tendency in chronic hypoxemia in comparison with other amino acids conspicuously. Fetal plasma concentrations of the glycogenetic amino acids, that were significantly decreased under maternal starvation, did not show a decrease tendency in chronic hypoxemia. Less