Currently, a search for selective antagonists of luteinizing hormone (LH) receptor, which are required to suppress the steroidogenesis in hormone-dependent tumors and to prevent the ovarian hyperstimulation syndrome, is carried out. One approach to tackle this problem is the development of low-molecular-weight antagonists of the allosteric site of this receptor, which is located in its transmembrane domain. The aim of this work was to develop the heterocyclic compounds, the derivatives of thieno[2,3-d]pyrimidine (TP31), pyrimido[4,5,6-de][1,6]naphthyridine (PP10), and pyrido[3,4-d]pyrimidine (PP17), and to study their ability to affect the functional activity of the LH receptor in the in vitro and in vivo conditions. It was shown that TP31 at micromolar concentrations suppressed stimulating effects of human chorionic gonadotropin (hCG) and TP03, an allosteric agonist of the LH receptor, on the adenylyl cyclase activity in rat testicular membranes; its effect was most pronounced in relation to the stimulating effects of TP03. This was due to a higher selectivity of the TP31 antagonist with respect to the cAMP-dependent signaling cascades, predominantly activated by TP03 and realized through Gs proteins. PP17 inhibited stimulatory effects of hCG and TP03 on the adenylyl cyclase activity to a similar extent but was less active compared to TP31. Upon intratesticular (10 mg/kg) or intraperitoneal (45 mg/kg) administration to male rats, TP31 and PP17 decreased the baseline plasma level of testosterone and inhibited the testosterone production stimulated by hCG (100 IU/rat); the inhibitory effect of TP31 was much more pronounced than that of PP17. PP10 exhibited a weaker antagonistic activity than TP31 and PP17 in the in vitro and in vivo conditions. The data obtained indicated that TP31, the most active functional antagonist among the studied compounds, binded to the allosteric site of the LH receptor, made it less accessible to allosteric agonists and impairs the hormonal signal transduction through the LH receptor. This suggests the prospects of the development of TP31-based inhibitors of LH-dependent pathways and steroidogenesis.

中文翻译：

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具有拮抗剂活性的促黄体激素受体的低分子量配体

目前，正在寻找黄体生成素 (LH) 受体的选择性拮抗剂，这是抑制激素依赖性肿瘤中的类固醇生成和预防卵巢过度刺激综合征所必需的。解决这个问题的一种方法是开发该受体变构位点的低分子量拮抗剂，该位点位于其跨膜结构域。这项工作的目的是开发杂环化合物、噻吩并 [2,3-d] 嘧啶 (TP31)、嘧啶并[4,5,6-de][1,6] 萘啶 (PP10) 和吡啶并[3,4-d] 嘧啶 (PP17)，并研究它们在体外和体内条件下影响 LH 受体功能活性的能力。结果表明，微摩尔浓度的 TP31 抑制了人绒毛膜促性腺激素 (hCG) 和 TPO3 的刺激作用，LH 受体的变构激动剂，对大鼠睾丸膜中的腺苷酸环化酶活性有影响；其作用在 TP03 的刺激作用中最为显着。这是由于 TP31 拮抗剂相对于 cAMP 依赖性信号级联具有更高的选择性，主要由 TP03 激活并通过 Gs 蛋白实现。PP17 在相似程度上抑制 hCG 和 TPO3 对腺苷酸环化酶活性的刺激作用，但与 TP31 相比活性较低。在雄性大鼠睾丸内 (10 mg/kg) 或腹腔内 (45 mg/kg) 给药后，TP31 和 PP17 降低了基线血浆睾酮水平，并抑制了 hCG (100 IU/大鼠) 刺激的睾酮产生；TP31 的抑制作用比 PP17 明显得多。在体外和体内条件下，PP10 表现出比 TP31 和 PP17 弱的拮抗活性。获得的数据表明，TP31 是所研究化合物中最活跃的功能性拮抗剂，它与 LH 受体的变构位点结合，使其不易被变构激动剂接近，并削弱了通过 LH 受体的激素信号转导。这表明基于 TP31 的 LH 依赖性途径和类固醇生成抑制剂的开发前景。