2-Thiouracil   中文名称: 硫脲嘧啶

Selective inhibitor of neuronal nitric oxide synthase (nNOS). Competitive inhibition with a Ki of 20 μM. Shows low activity against inducible NOS (iNOS, <25% inhibition at 500 μM) and endothelial NOS (eNOS, <15% inhibition at 500 μM). [1]

重组大鼠 nNOS 与 TU 孵育后，通过 L-[14C]瓜氨酸生成测定法测得，其酶活性受到浓度依赖性抑制，IC50 为 50 ± 5 μM。[1]
在测定条件下，1 mM 的 TU 可使重组 nNOS 的 NO 生成（通过硝酸盐/亚硝酸盐积累测量）抑制 51 ± 2%。[1]
在 100 μM 浓度下，TU 在缺乏 L-精氨酸和四氢生物蝶呤 (BH4) 的条件下，可抑制约 60% 的 nNOS 产生的 H2O2。这种抑制对氧合酶结构域活性具有特异性，因为在相同浓度下，TU 不影响 nNOS 的细胞色素 c 还原酶活性（还原酶结构域功能）。[1]
低温度 SDS-PAGE 实验证明，TU (500 μM) 拮抗了 BH4 诱导的 nNOS 二聚化，减少了在 1 μM BH4 存在下形成的 320 kDa 二聚体条带量。当 BH4 浓度提高到 10 μM 时，这种对二聚化的抑制作用被消除。[1]

主要的 NOS 活性测定中，将重组 nNOS 在含有 Tris-HCl 缓冲液 (pH 7)、NADPH、氯化钙、BH4、钙调蛋白、FAD、FMN 和 L-[U-14C]精氨酸的反应混合物中于 37°C 孵育 15 分钟。反应用冰冷的 HEPES/EDTA 缓冲液终止。然后将混合物通过阳离子交换柱以保留未反应的精氨酸。形成的 [14C]瓜氨酸用水洗脱，并通过液体闪烁计数法定量，以确定酶活性。[1]
NO 生成也可以通过测量其代谢物硝酸盐和亚硝酸盐来评估。将重组 nNOS 与包括 L-精氨酸在内的反应组分一起孵育，使用商业比色测试试剂盒定量培养基中积累的硝酸盐/亚硝酸盐。[1]
nNOS 产生的 H2O2 使用硫氰酸亚铁法测定。[1]
nNOS 的细胞色素 c 还原酶活性通过在缺乏钙和钙调蛋白的条件下，分光光度法监测 NADPH 依赖的细胞色素 c 还原来测量。[1]

Absorption, Distribution and Excretion
Drug delivery to the fetus: Time to fetal presence: 10 minutes; Time to reach fetal/maternal concentration equilibrium: 40 minutes; Fetal/maternal concentration ratio of 1.0 /Excerpt from Table/
/In rats/ (35)S-labeled accumulation was faster and more extensive starting from smaller doses, indicating a saturable transport mechanism. Similar studies using (14)C-thiouracil showed radioactive accumulation in the thyroid tissue of both mother rabbits and fetuses…
…Whether using large doses (39 μmol) or small doses (1.2 μmol) of (35)S-thiouracil, the total radioactivity and accumulation of unmetabolized (35)S-thiouracil in thyroid tissue were significantly higher than in rat plasma compared to plasma levels.
Thiouracil can be absorbed through the rat gastrointestinal tract… After intravenous injection of 5 mg thiouracil in rats, only 30% of the thiouracil was recovered from the cadaver 3 hours later, with the remainder being trace amounts. 24 hours later.
For more data on the absorption, distribution and excretion (complete) of 2-thiouracil (7 metabolites), please visit the HSDB record page.

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Metabolism/Metabolites
In homogenized liver preparations from female Holtzman rats, 28-35% of thiouracil was metabolized within 3 hours. The degradation pathway of thiouracil is presumed to be: uracil; β-urea propionic acid, which is further metabolized to β-alanine; ammonia and carbon dioxide…

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The stability of thiouracil under the assay conditions was evaluated by high performance liquid chromatography (HPLC). Incubation of TU (500 μM) with high concentrations of BH4 (up to 100 μM) did not result in significant degradation, confirming its stability during enzyme activity assays. [1]

[1]. 2-thiouracil is a selective inhibitor of neuronal nitric oxide synthase antagonising tetrahydrobiopterin-dependent enzyme activation and dimerisation. FEBS Lett, 2000. 485(2-3): p. 109-12.

[2]. Mechanism of selective incorporation of the melanoma seeker 2-thiouracil into growing melanin. J Med Chem, 1996. 39(26): p. 5192-201.

According to the International Agency for Research on Cancer (IARC) of the World Health Organization, thiouracil is potentially carcinogenic. Thiouracil is a nucleobase analog, a derivative of uracil in which the oxygen group at the C-2 position is replaced by a thio group. It is both an antithyroid drug and a metabolite. It is a thiocarbonyl compound and also a nucleobase analog. It is functionally related to uracil. 2-Thiouracil has been reported in Euglena gracilis, and relevant data are available. Thiouracil is a thiouracil-containing compound. As a known antithyroid drug and a highly selective nitric oxide synthase (NOS) inhibitor, thiouracil can also covalently bind to dopaquinone, produced by tyrosinase-catalyzed tyrosine oxidation, thereby selectively accumulating in newly synthesized melanin in overactive melanocytes and providing a method for locating melanoma cells. (NCI04) It is found in the seeds of Brassica and Cruciferae plants. Thiouracil was once used as an antithyroid drug, a coronary vasodilator, and a treatment for congestive heart failure, but its use has been largely superseded by other drugs. It is known to cause blood disorders and is suspected of being teratogenic and carcinogenic.

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Mechanism of Action
Antithyroid drugs primarily inhibit the formation of thyroid hormones by interfering with the organification of iodine. This means they interfere with the oxidation of iodide ions, but the detailed mechanism is difficult to elucidate due to incomplete understanding of the thyroid iodine oxidation system. /Antithyroid Drugs/
Thiodamide derivatives do not have permanent effects on the thyroid gland but inhibit hormone synthesis and secretion until spontaneous remission occurs during the disease process. /Thiodamide Derivatives/

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Therapeutic Uses
Antimetabolites; Antithyroid Drugs; Vasodilators
Thiodamide has been reported as an antithyroid drug in human medicine and for the treatment of angina and congestive heart failure… However, there is no evidence that thiodamide is currently used for these purposes in the United States.
Treatment for hyperthyroidism; angina pectoris; congestive heart failure / Previous use in China: USA /
Drugs (Veterinary): Thyroid inhibitors; used to treat hyperthyroidism and promote weight gain
Drug Warnings
The main disadvantage of antithyroid drug treatment is the high relapse rate after discontinuation. /Antithyroid Drugs/
Patients should immediately report sore throat or fever, which is often a precursor to agranulocytosis. If mild granulocytopenia is found, it may be a sign of thyrotoxicosis or the first symptom of this dangerous drug reaction. Caution and frequent white blood cell counts are necessary in this case. Thiamine derivatives: Women taking these drugs should not breastfeed their infants. Antithyroid drugs: It is unclear at what stage of pregnancy treatment will affect the fetus (fetal goiter and hypothyroidism), but in some cases, medication is not started until two-thirds of the pregnancy. Even later maternal medication may cause this. /Antithyroid Drugs/
For more drug warnings (full) data on 2-thiouracil (6 of them), please visit the HSDB record page.

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2-thiouracil is an approved antithyroid drug and is also an investigational drug for the detection and targeting of metastatic melanoma. Its antithyroid and melanoma-targeting properties are related to its inhibitory effects on enzymes such as thyroid iodine peroxidase, myeloperoxidase, eosinophil peroxidase, and tyrosinase. [1]
Given the presence of NOS activity in the thyroid gland, the newly discovered TU’s properties as a selective nNOS inhibitor may help in understanding its antithyroid effects. It also represents a potential lead compound for the development of neuroprotective agents. [1]
This inhibition competes with L-arginine. Increasing the concentration of the cofactor tetrahydrobiopterin (BH4) can reverse this inhibition, suggesting that the compound interacts with or is adjacent to the BH4 binding site. The sulfur atom in the thiourea moiety is crucial for reactivity, since both uracil (which lacks sulfur) and thiourea are ineffective. [1]

C4H4N2OS

128.15236

128.004

141-90-2

2-Thiouracil-13C,15N2

1269845

White to off-white solid powder

1.5±0.1 g/cm3

337.2ºC at 760mmHg

>300 °C(lit.)

157.7ºC

5.45E-05mmHg at 25°C

1.678

-0.28

80.74

2

2

0

8

163

0

ZEMGGZBWXRYJHK-UHFFFAOYSA-N

InChI=1S/C4H4N2OS/c7-3-1-2-5-4(8)6-3/h1-2H,(H2,5,6,7,8)

2-sulfanylidene-1H-pyrimidin-4-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~50 mg/mL (~390.17 mM)
H2O : ~0.67 mg/mL (~5.23 mM)

配方 1 中的溶解度: ≥ 3.75 mg/mL (29.26 mM) (饱和度未知) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (这些助溶剂从左到右依次添加，逐一添加), 澄清溶液。
例如，若需制备1 mL的工作液，可将100 μL 37.5 mg/mL 澄清的 DMSO 储备液加入到400 μL PEG300中，混匀；再向上述溶液中加入50 μL Tween-80，混匀；然后加入450 μL 生理盐水定容至1 mL。
*生理盐水的制备：将 0.9 g 氯化钠溶解在 100 mL ddH₂O中，得到澄清溶液。

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配方 2 中的溶解度: ≥ 3.75 mg/mL (29.26 mM) (饱和度未知) in 10% DMSO + 90% Corn Oil (这些助溶剂从左到右依次添加，逐一添加), 澄清溶液。
例如，若需制备1 mL的工作液，可将 100 μL 37.5 mg/mL 的澄清 DMSO 储备液加入到 900 μL 玉米油中并混合均匀。

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请根据您的实验动物和给药方式选择适当的溶解配方/方案：
1、请先配制澄清的储备液(如：用DMSO配置50 或 100 mg/mL母液(储备液));
2、取适量母液，按从左到右的顺序依次添加助溶剂，澄清后再加入下一助溶剂。以 下列配方为例说明 (注意此配方只用于说明，并不一定代表此产品 的实际溶解配方):
10% DMSO → 40% PEG300 → 5% Tween-80 → 45% ddH2O (或 saline);
假设最终工作液的体积为 1 mL, 浓度为5 mg/mL: 取 100 μL 50 mg/mL 的澄清 DMSO 储备液加到 400 μL PEG300 中，混合均匀/澄清；向上述体系中加入50 μL Tween-80，混合均匀/澄清；然后继续加入450 μL ddH2O (或 saline)定容至 1 mL；
3、溶剂前显示的百分比是指该溶剂在最终溶液/工作液中的体积所占比例;
4、 如产品在配制过程中出现沉淀/析出，可通过加热(≤50℃)或超声的方式助溶;
5、为保证最佳实验结果，工作液请现配现用！
6、如不确定怎么将母液配置成体内动物实验的工作液，请查看说明书或联系我们;
7、 以上所有助溶剂都可在 Invivochem.cn网站购买。