Buu N T, Lussier C
Laboratory of the Autonomic Nervous System, Clinical Research Institute of Montreal, Quebec, Canada.
Am J Physiol. 1990 Feb;258(2 Pt 2):F287-91. doi: 10.1152/ajprenal.1990.258.2.F287.
The hypothesis that dopamine (DA) is involved in the control of aldosterone secretion is given some support by the finding of DA in the adrenal cortex of several species, but the source of this DA is not known. This study showed that the administration of L-dopa to intact rats or medullectomized rats caused a significant DA increase in the adrenal cortex. The DA increase in the cortex was more pronounced than in the medulla, coincident with higher L-dopa uptake by the cortical tissue. Tyrosine administration raised DA levels only in the medulla. Sympathectomy of the rat by 6-hydroxydopamine treatment did not affect DA basal levels in the cortex or the DA increase in this tissue after L-dopa injection. 3,4-Dihydroxyphenylacetic acid (DOPAC) is detectable in the adrenal cortex but not in the adrenal medulla, and DOPAC levels increased significantly after L-dopa, which indicates monoamine oxidase (MAO) activity within the adrenal cortex. Because 6-hydroxydopamine pretreatment did not alter DOPAC levels, cortical MAO may be located outside catecholaminergic neurons. The results established circulating L-dopa as a precursor for DA in the adrenal cortex of the rat. They also showed that tyrosine hydroxylase activity is absent from the adrenal cortex of this species.
多巴胺（DA）参与醛固酮分泌调控这一假说，因在几种动物的肾上腺皮质中发现DA而得到一定支持，但该DA的来源尚不清楚。本研究表明，给完整大鼠或去髓质大鼠注射左旋多巴会使肾上腺皮质中的DA显著增加。皮质中DA的增加比髓质更明显，这与皮质组织对左旋多巴的摄取更高相一致。给予酪氨酸仅使髓质中的DA水平升高。用6-羟基多巴胺处理使大鼠交感神经切除，并不影响皮质中DA的基础水平，也不影响注射左旋多巴后该组织中DA的增加。在肾上腺皮质中可检测到3,4-二羟基苯乙酸（DOPAC），但在肾上腺髓质中未检测到，且注射左旋多巴后DOPAC水平显著升高，这表明肾上腺皮质内存在单胺氧化酶（MAO）活性。由于6-羟基多巴胺预处理并未改变DOPAC水平，所以皮质MAO可能位于儿茶酚胺能神经元之外。这些结果证实循环中的左旋多巴是大鼠肾上腺皮质中DA的前体。它们还表明该物种的肾上腺皮质中不存在酪氨酸羟化酶活性。
