Riquelme R A, Llanos J A, McGarrigle H H, Sanhueza E M, Hanson M A, Giussani D A
Campus Oriente, Instituto de Ciencias Biomédicas, Facultad de Medicina, International Center for Andean Research, Universidad de Chile, Santiago.
Endocrinology. 1998 May;139(5):2564-70. doi: 10.1210/endo.139.5.6010.
This study tested the hypothesis that the fetal llama, a species adapted to the chronic hypoxia of life at high altitude, demonstrates a potent carotid chemoreflex influence on adrenocortical responses during acute hypoxemia. Plasma ACTH and cortisol concentrations, and mesencephalic and adrenal blood flows were measured during a 1-h period of acute hypoxemia in six intact and four carotid sinus-denervated llama fetuses at 0.6-0.7 of gestation. Fetal PaO2 was reduced from approximately 23 to about 14 mm Hg in both intact and carotid-denervated groups during acute hypoxemia. During hypoxemia, fetal plasma ACTH, adrenal blood flow, and, therefore, delivery of ACTH to the adrenals increased to similar extents in both intact and carotid-denervated fetal llamas. Despite this, the increase in plasma cortisol in hypoxemia in intact fetuses was absent in carotid-denervated fetuses. In addition, the increase in delivery of cortisol to the mesencephalon calculated in intact fetuses during hypoxemia did not occur in the carotid-denervated group. These data suggest that the integrity of the carotid chemoreceptors is indispensable to cortisol release during acute hypoxemia in the llama fetus, even at 0.6-0.7 of gestation.
骆马胎儿作为一种适应高海拔地区慢性低氧生活的物种，在急性低氧血症期间，其颈动脉化学反射对肾上腺皮质反应具有强大影响。在妊娠0.6 - 0.7期，对6只完整的和4只颈动脉窦去神经支配的骆马胎儿进行了1小时急性低氧血症期间的血浆促肾上腺皮质激素（ACTH）和皮质醇浓度、中脑及肾上腺血流量测量。在急性低氧血症期间，完整组和颈动脉去神经支配组的胎儿动脉血氧分压（PaO2）均从约23毫米汞柱降至约14毫米汞柱。在低氧血症期间，完整的和颈动脉去神经支配的骆马胎儿血浆ACTH、肾上腺血流量以及因此ACTH向肾上腺的输送量均以相似程度增加。尽管如此，颈动脉去神经支配的胎儿在低氧血症时血浆皮质醇未增加，而完整胎儿有增加。此外，低氧血症期间完整胎儿计算得出的皮质醇向中脑输送量的增加在颈动脉去神经支配组未出现。这些数据表明，即使在妊娠0.6 - 0.7期，颈动脉化学感受器的完整性对于骆马胎儿急性低氧血症期间皮质醇的释放也是不可或缺的。
