Hitsumoto Y, Saheki S, Kitagawa H, Yano J, Matsuura S
Department of Obstetrics and Gynecology, Ehime University School of Medicine, Japan.
J Endocrinol. 1996 Aug;150(2):243-53. doi: 10.1677/joe.0.1500243.
Nitric oxide (NO) is involved in the regulation of endocrine functions, but only a few studies have been reported about its role in placental hormone secretion. We investigated whether NO has any function in the release of human chorionic gonadotropin (hCG) in two different choriocarcinoma cell lines, JEG-3 and BeWo. First, nitric oxide synthase (NOS) was characterized in the choriocarcinoma cells. NOS activity was localized mainly in the particulate fraction and depended on calcium/calmodulin. Activity was inhibited by the presence of the L-arginine analog, NG-monomethyl-L-arginine (L-NMMA; 1 x 10(-4) M). Western blot analysis showed that the choriocarcinoma cells contained an endothelial isoform of NOS. The NO donor, sodium nitroprusside (SNP; 1 x 10(-5) and 1 x 10(-4) M), significantly inhibited hCG secretion in both choriocarcinoma cell lines. The suppression of hCG release by SNP (1 x 10(-5) M) was blocked by the addition of an NO scavenger, hemoglobin (1 x 10(-6) M). L-Arginine (1 x 10(-2) M), a NOS substrate, inhibited basal hCG secretion in JEG-3 cells. Incubation of the cells with L-NMMA (1 x 10(-4) and 1 x 10(-3) M) significantly increased hCG release. Exposure of both cell lines to increasing concentrations of a cyclic GMP analog (8-bromo-cyclic GMP; 1 x 10(-4) to 1 x 10(-2) M) caused a dose-dependent inhibition of hCG release. Cyclic GMP accumulation in response to SNP (1 x 10(-4) M), however, was not detected in either JEG-3 or BeWo cells. These data demonstrated that the endothelial isoform of NOS and a functional L-arginine-NO pathway are present in the choriocarcinoma cell lines. In addition, these findings support the hypothesis that NO produced in these cell lines is involved in the regulation of hCG secretion. We assume that although cyclic GMP is likely to play a role as a second messenger, a cyclic GMP-independent pathway cannot be excluded as a possible physiological mechanism in the attenuation of hCG release by NO.
一氧化氮（NO）参与内分泌功能的调节，但关于其在胎盘激素分泌中的作用，仅有少数研究报道。我们研究了NO在两种不同的绒毛膜癌细胞系JEG - 3和BeWo中对人绒毛膜促性腺激素（hCG）释放是否有作用。首先，对绒毛膜癌细胞中的一氧化氮合酶（NOS）进行了表征。NOS活性主要定位于微粒部分，且依赖于钙/钙调蛋白。L - 精氨酸类似物NG - 单甲基 - L - 精氨酸（L - NMMA；1×10⁻⁴ M）的存在可抑制其活性。蛋白质免疫印迹分析表明，绒毛膜癌细胞含有NOS的内皮型同工酶。NO供体硝普钠（SNP；1×10⁻⁵和1×10⁻⁴ M）显著抑制了两种绒毛膜癌细胞系中的hCG分泌。添加NO清除剂血红蛋白（1×10⁻⁶ M）可阻断SNP（1×10⁻⁵ M）对hCG释放的抑制作用。NOS底物L - 精氨酸（1×10⁻² M）抑制了JEG - 3细胞中的基础hCG分泌。用L - NMMA（1×10⁻⁴和1×10⁻³ M）处理细胞可显著增加hCG释放。将两种细胞系暴露于浓度递增的环鸟苷酸类似物（8 - 溴环鸟苷酸；1×10⁻⁴至1×10⁻² M）中会导致hCG释放呈剂量依赖性抑制。然而，在JEG - 3或BeWo细胞中均未检测到对SNP（1×10⁻⁴ M）的环鸟苷酸积累反应。这些数据表明，NOS的内皮型同工酶和功能性L - 精氨酸 - NO途径存在于绒毛膜癌细胞系中。此外，这些发现支持了这些细胞系中产生的NO参与hCG分泌调节的假说。我们推测，尽管环鸟苷酸可能作为第二信使发挥作用，但在NO减弱hCG释放的过程中，不能排除存在不依赖环鸟苷酸的途径作为一种可能的生理机制。
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