Simonetta G, Young I R, McMillen I C
Department of Physiology, University of Adelaide, Australia.
J Auton Nerv Syst. 1996 Sep 12;60(3):108-14. doi: 10.1016/0165-1838(96)00026-4.
We have investigated whether removal of the fetal adrenal glands alters the effect of acute hypoxaemia on the circulating concentrations of noradrenaline, adrenaline, Met-Enkephalin and Met-Enkephalin-Arg6-Phe7 (MERF) in the late gestation sheep fetus. Ewes of 6 adrenalectomized and 9 intact fetuses were subjected to a 30 min period of hypoxaemia and a 30 min period of normoxaemia between 135 and 141 days gestation. Removal of the fetal adrenals abolished the fetal adrenaline response and significantly reduced the fetal noradrenaline response to hypoxaemia. There was no significant increase in circulating Met-Enkephalin during either hypoxaemia or normoxaemia in either the intact and adrenalectomized groups. During basal conditions, plasma concentrations of MERF were significantly greater in the adrenalectomized group (1.64 +/- 0.07 ng/ml) than in the intact fetal sheep (1.04 +/- 0.05 ng/ml). There were significantly greater changes (p < 0.05) in plasma MERF concentrations during hypoxaemia than during normoxaemia in both the intact and adrenalectomized groups. Plasma concentrations of MERF were inversely correlated with arterial PO2 (r = -0.44, p < 0.01) in the adrenalectomized but not the intact group of fetal sheep during hypoxaemia. We have demonstrated therefore that the fetal adrenal is the major source of circulating catecholamines, but not Met-Enkephalin or MERF during hypoxaemia in late gestation. The increase in circulating MERF concentrations after adrenalectomy may reflect compensatory changes in the synthesis and/or secretion of MERF in developing sympathetic neurones.
我们研究了摘除胎儿肾上腺是否会改变急性低氧血症对妊娠晚期绵羊胎儿循环中去甲肾上腺素、肾上腺素、甲硫氨酸脑啡肽和甲硫氨酸脑啡肽-精氨酸6-苯丙氨酸7（MERF）浓度的影响。在妊娠135至141天期间，对6只摘除肾上腺和9只未摘除肾上腺的胎儿的母羊进行了30分钟的低氧血症期和30分钟的正常氧血症期。摘除胎儿肾上腺消除了胎儿的肾上腺素反应，并显著降低了胎儿对低氧血症的去甲肾上腺素反应。在未摘除肾上腺组和摘除肾上腺组中，无论是低氧血症期还是正常氧血症期，循环中的甲硫氨酸脑啡肽均未显著增加。在基础状态下，摘除肾上腺组的血浆MERF浓度（1.64±0.07 ng/ml）显著高于未摘除肾上腺的胎儿绵羊组（1.04±0.05 ng/ml）。在未摘除肾上腺组和摘除肾上腺组中，低氧血症期血浆MERF浓度的变化均显著大于正常氧血症期（p<0.05）。在低氧血症期间，摘除肾上腺的胎儿绵羊组血浆MERF浓度与动脉血氧分压呈负相关（r = -0.44，p<0.01），而未摘除肾上腺组则无此相关性。因此，我们证明了胎儿肾上腺是妊娠晚期低氧血症期间循环儿茶酚胺的主要来源，但不是甲硫氨酸脑啡肽或MERF的主要来源。肾上腺切除术后循环中MERF浓度的增加可能反映了发育中的交感神经元中MERF合成和/或分泌的代偿性变化。
