Regulation of Adrenal Vascular Tone by Steroidogenic Cells

描述(申请人提供)：醛固酮是由肾上腺皮质的球状带细胞合成的。它调节钠钾平衡，与高血压、心肌肥厚和充血性心力衰竭有关。血管紧张素II(ALL)、促肾上腺皮质激素(ACTH)和钾(K)是醛固酮释放的主要刺激因素。流向肾上腺皮质的血液将营养物质输送到ZG细胞，并将醛固酮输送到其目标组织。因此，了解调节肾上腺血流量(ABF)和肾上腺血管张力的因素是很重要的。ACTH在体内扩张肾上腺血管，增加ABF；然而，ACTH在体外不能松弛分离的肾上腺皮质动脉。我们想知道是否肾上腺皮质中的其他细胞释放了一种血管扩张剂，介导了ACTH的扩张。当ZG细胞与分离的肾上腺动脉共同孵育时，ACTH引起松弛。高钾通道阻断剂、细胞色素P450阻断剂和环氧二十碳三烯酸(EET)拮抗剂可抑制ZG细胞对ACTH的依赖性松弛。ZG细胞同样增强了肾上腺动脉对AII的松弛作用。ZG细胞条件培养液(ZG-CM)也可松弛肾上腺动脉，并持续释放EETs和前列腺素。这些研究表明，ZG细胞释放一种可溶性因子(S)，介导对ACTH和ALL的松弛。该因子(S)可能是EET或相关的脂肪酸代谢产物(S)。我们将检验这样一种假设，即ZG细胞在解剖上与肾上腺皮质中的肾上腺动脉非常接近，会释放导致血管扩张的可溶的、可转移的因子。这些研究将探讨ZG细胞和ZG-CM在体外松弛离体牛肾上腺皮质动脉的能力，并介导ACTH和ALL诱导的扩张。各种脂肪酸以及已知的内源性扩张剂的抑制剂将被测试。将对束状带(ZF)细胞进行平行研究。为了保持ZG细胞和肾上腺动脉之间的解剖关系，将进行平行研究，将灌流的肾上腺动脉嵌入肾上腺皮质切片中。从ZG-CM提取物中分离鉴定活性成分(S)。该因子(S)将被合成并测试扩张器的活性。此外，还将检测该因子(S)对钾通道活性和平滑肌细胞膜电位的影响。我们将测定促肾上腺皮质激素和所有刺激下ZG细胞释放S因子的情况。还将在麻醉大鼠身上进行体内研究，以确定ZG细胞因子(S)在调节ABF中的作用。用激光多普勒血流计测量ACTH和ALL对皮质ABF的反应，并确定内源性血管扩张途径抑制剂的作用。ZG细胞对肾上腺血管张力的调节可能具有更广泛的意义。这可能代表了许多内分泌腺调节血管张力的一般途径。

DESCRIPTION (provided by applicant): Aldosterone is synthesized by zona glomerulosa (ZG) cells of the adrenal cortex. It regulates sodium and potassium (K) balance and is involved hypertension, cardiac hypertrophy and congestive heart failure. Angiotensin II (All), adrenocorticotropic hormone (ACTH) and potassium (K) are major stimuli for aldosterone release. Blood flow to the adrenal cortex delivers nutrients to ZG cells and carries aldosterone to its target tissues. Thus, understanding the factors regulating adrenal blood flow (ABF) and adrenal vascular tone is important. ACTH dilates the adrenal vasculature and increases ABF in vivo; however, ACTH does not relax isolated adrenal cortical arteries in vitro. We wondered if other cells in the adrenal cortex released a vasodilator that mediates the dilation by ACTH. When ZG cells were co-incubated with the isolated adrenal arteries, ACTH caused relaxation. The ZG cell-dependent relaxations to ACTH were inhibited by high extracellular K, a K channel inhibitor, a cytochrome P450 inhibitor and an epoxyeicosatrienoic acid (EET) antagonist. ZG cells similarly enhanced the relaxation of adrenal arteries to AII. ZG cell conditioned media (ZG-CM) also relaxed adrenal arteries and continued EETs and prostaglandins. These studies indicate that ZG cells release a soluble factor(s) that mediates the relaxations to ACTH and All. This factor(s) may be an EET or related fatty acid metabolite(s). We will test the hypothesis that ZG cells, which are in close anatomical proximity to adrenal arteries in the adrenal cortex, release soluble, transferable factors that cause vasodilation. The proposed studies will investigate the ability of ZG cells and ZG-CM to relax isolated bovine adrenal cortical arteries in vitro and mediate ACTH- and All-induced dilation. Various fatty acids as well as inhibitors of known endogenous dilators will be tested. Parallel studies will be conducted on zona fasciculata (ZF) cells. To maintain the anatomical relationship between ZG cells and adrenal arteries, parallel studies will be conducted with perfused adrenal arteries embedded in slices of the adrenal cortex. The active factor(s) will be isolated and identified from ZG-CM extracts using HPLC and mass spectrometry. The factor(s) will be synthesized and tested for dilator activity. The action of the factor(s) will also be tested on K channel activity and smooth muscle cell membrane potential. We will measure the release of the factor(s) from ZG cells with ACTH and All stimulation. Studies will also be performed in vivo in anesthetized rats to determine the role of the ZG cell factor(s) in regulating ABF. Cortical ABF will be measured by a laser Doppler flowmeter in response to ACTH and All and the effect of inhibitors of endogenous vasodilator pathways determined. The regulation of adrenal vascular tone by ZG cells may have broader implications. This may represent a general pathway for regulation of vascular tone in many endocrine glands.