Carter A M, Homan J, Fraser M, Richardson B S, Challis J R
Department of Obstetrics and Gynecology, Lawson Research Institute, University of Western Ontario, London, Canada.
Am J Physiol. 1995 Sep;269(3 Pt 1):E598-604. doi: 10.1152/ajpendo.1995.269.3.E598.
To examine the role of endogenous adrenocorticotropic hormone (ACTH) in adrenal blood flow responses to hypoxia, we studied unanesthetized ovine fetuses during an intravenous infusion of cortisol or vehicle. Fetal hypoxia was induced after 5 h of cortisol or vehicle infusion. Control fetuses were not made hypoxic. Blood flows were determined before and at three time points during the infusions. At 2 and 6 h of hypoxia, in vehicle-infused fetuses, fetal plasma concentrations of immunoreactive ACTH (irACTH) had risen from 9 +/- 3 (SE) pg/ml to 68 +/- 25 and 127 +/- 37 pg/ml, respectively. No significant change in fetal plasma irACTH occurred in the other groups. Adrenal cortical blood flow rose three- to fourfold during hypoxia in vehicle-infused fetuses but did not change from prehypoxia levels in cortisol-infused fetuses (P < 0.005). Medullary flow rose with hypoxemia, and this was not affected by concurrent cortisol infusion. Adrenal blood flows did not change in the control groups. Thus prior infusion of cortisol suppressed the rise in fetal plasma ACTH during hypoxia and selectively blocked the increase in adrenal cortical blood flow.
为研究内源性促肾上腺皮质激素（ACTH）在肾上腺对缺氧血流反应中的作用，我们在静脉输注皮质醇或赋形剂期间，对未麻醉的绵羊胎儿进行了研究。在输注皮质醇或赋形剂5小时后诱导胎儿缺氧。对照胎儿不进行缺氧处理。在输注前及输注期间的三个时间点测定血流。在缺氧2小时和6小时时，在输注赋形剂的胎儿中，胎儿血浆免疫反应性ACTH（irACTH）浓度分别从9±3（标准误）pg/ml升至68±25和127±37 pg/ml。其他组胎儿血浆irACTH无显著变化。在输注赋形剂的胎儿中，缺氧期间肾上腺皮质血流增加了三到四倍，但在输注皮质醇的胎儿中，肾上腺皮质血流未从缺氧前水平发生变化（P<0.005）。髓质血流随低氧血症而增加，且不受同时输注皮质醇的影响。对照组肾上腺血流无变化。因此，预先输注皮质醇可抑制缺氧期间胎儿血浆ACTH的升高，并选择性地阻断肾上腺皮质血流的增加。
