Guiang S F, Widness J A, Flanagan K B, Schmidt R L, Radmer W J, Georgieff M K
Department of Pediatrics, University of Minnesota School of Medicine, Minneapolis.
J Dev Physiol. 1993 Mar;19(3):99-104.
Myoglobin, a hemoprotein found in abundance in the muscle of postnatal animals, increases in concentration in response to hypoxia, thereby protecting tissue from damage. Fetuses exposed to intrauterine hypoxemia are also susceptible to organ damage, but the response of fetal muscle myoglobin to hypoxemia is unknown. To study whether fetal muscle myoglobin concentrations are elevated following intrauterine hypoxemia, we exposed eight chronically catheterized late gestation sheep to a wide range of fetal oxygen levels over 15 to 30 days and correlated the level of fetal oxygenation with heart and skeletal muscle myoglobin concentrations measured at sacrifice. A lower level of fetal oxygenation, expressed as the integrated area under the arterial saturation (SaO2)-time curve, was associated with greater myocardial myoglobin concentration (r = 0.90; P < 0.01). This relationship was not observed for skeletal muscle (r = 0.43; P = ns). A lower level of fetal oxygenation was associated with lower myoglobin:iron (w/w) ratio in skeletal muscle (r = 0.71; P < 0.03), implying less incorporation of iron into myoglobin. A similar relationship was not apparent for cardiac tissue. The higher myocardial myoglobin concentrations found in the more hypoxic fetuses were consistent with previous observations in postnatal animals. This likely represents an intracellular compensatory mechanism for sustaining short-term mitochondrial oxygen delivery in a critical organ with a high rate of oxygen consumption. The lack of myoglobin responsiveness to hypoxia in fetal skeletal muscle may be due to its much lower oxygen consumption rate and activity level.
肌红蛋白是一种在出生后动物肌肉中大量存在的血红素蛋白，其浓度会因缺氧而升高，从而保护组织免受损伤。暴露于子宫内低氧血症的胎儿也易受器官损伤，但胎儿肌肉肌红蛋白对低氧血症的反应尚不清楚。为了研究子宫内低氧血症后胎儿肌肉肌红蛋白浓度是否升高，我们将8只长期插管的妊娠晚期绵羊在15至30天内暴露于广泛的胎儿氧水平，并将胎儿氧合水平与处死时测量的心脏和骨骼肌肌红蛋白浓度相关联。以动脉血氧饱和度（SaO2）-时间曲线下的积分面积表示的较低胎儿氧合水平与较高的心肌肌红蛋白浓度相关（r = 0.90；P < 0.01）。骨骼肌未观察到这种关系（r = 0.43；P = 无显著性差异）。较低的胎儿氧合水平与骨骼肌中较低的肌红蛋白：铁（重量/重量）比值相关（r = 0.71；P < 0.03），这意味着铁掺入肌红蛋白的量较少。心脏组织未出现类似关系。在缺氧程度较高的胎儿中发现的较高心肌肌红蛋白浓度与先前在出生后动物中的观察结果一致。这可能代表了一种细胞内补偿机制，用于在一个氧消耗率高的关键器官中维持短期线粒体氧输送。胎儿骨骼肌中肌红蛋白对缺氧缺乏反应可能是由于其低得多的氧消耗率和活动水平。
