Regulation of Adrenal Vascular Tone by Steroidogenic Cells

描述（由申请人提供）：醛固酮由肾上腺皮质的肾小球带（ZG）细胞合成。它调节钠和钾(K)的平衡，并参与高血压，心脏肥厚和充血性心力衰竭。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物。血液流向肾上腺皮质，将营养物质输送到ZG细胞，并将醛固酮运送到目标组织。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重要的。ACTH扩张肾上腺血管，增加体内ABF；然而，ACTH不放松离体肾上腺皮质动脉。我们想知道肾上腺皮质中的其他细胞是否释放了一种血管舒张剂，通过ACTH介导血管舒张。当ZG细胞与离体肾上腺动脉共孵育时，ACTH引起松弛。高细胞外K、K通道抑制剂、细胞色素P450抑制剂和环氧二碳三烯酸（EET）拮抗剂可抑制ZG细胞对ACTH的依赖性松弛。ZG细胞同样增强肾上腺动脉对AII的松弛。ZG细胞条件培养基（ZG- cm）也能放松肾上腺动脉并持续eet和前列腺素。这些研究表明ZG细胞释放一种可溶性因子介导ACTH和All的松弛。这个因素可能是EET或相关的脂肪酸代谢物。我们将测试ZG细胞的假设，这些细胞在解剖学上接近肾上腺皮质的肾上腺动脉，释放可溶解的，可转移的因子，导致血管舒张。该研究将研究ZG细胞和ZG- cm在体外放松离体牛肾上腺皮质动脉的能力，以及介导ACTH和all诱导的扩张的能力。将测试各种脂肪酸以及已知内源性扩张剂的抑制剂。将对束状带（ZF）细胞进行平行研究。为了维持ZG细胞与肾上腺动脉的解剖关系，平行研究将在肾上腺皮质切片中包埋灌注的肾上腺动脉。使用HPLC和质谱法从ZG-CM提取物中分离和鉴定活性因子。将合成因子并测试扩张剂活性。该因子的作用还将在K通道活性和平滑肌细胞膜电位上进行测试。我们将测量在ACTH和All刺激下ZG细胞释放的因子。研究还将在麻醉大鼠体内进行，以确定ZG细胞因子在调节ABF中的作用。皮质ABF将通过激光多普勒流量计测量ACTH和All的反应，并确定内源性血管扩张剂途径抑制剂的作用。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体血管张力调节的一般途径。

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.