激素Hormone

激素通过与靶细胞上的特异受体结合发挥作用。水溶性的肽类激素（如胰岛素、胰高血糖素）和儿茶酚胺（如肾上腺素）不能穿过细胞膜，与膜受体结合后通过 cAMP、Ca²⁺ 等第二信使或酪氨酸激酶级联放大信号；脂溶性的类固醇激素（如皮质醇、雌二醇、睾酮）和甲状腺激素可进入细胞，与胞内受体结合后直接调控基因转录。激素分泌多受负反馈调节。

Hormones act by binding specific receptors on target cells. Water-soluble peptide hormones such as insulin and glucagon, and catecholamines such as adrenaline, cannot cross the membrane; they bind surface receptors and amplify the signal through second messengers such as cAMP and Ca²⁺ or tyrosine-kinase cascades. Lipid-soluble steroid hormones such as cortisol, oestradiol and testosterone, and thyroid hormones, enter the cell, bind intracellular receptors and regulate gene transcription directly. Secretion is usually under negative feedback control.

1902 年贝利斯和斯塔林发现小肠分泌的促胰液素能经血液刺激胰腺分泌，1905 年斯塔林提出 hormone 一词（希腊语“激发”）。1901 年高峰让吉和阿尔德里奇分离出肾上腺素。1921 年班廷和贝斯特提取出胰岛素，1955 年桑格测定胰岛素的氨基酸序列，这是第一个被测序的蛋白质。1965 年中国科学家首次人工合成具有生物活性的结晶牛胰岛素。

In 1902 Bayliss and Starling found that secretin from the small intestine stimulates the pancreas via the blood, and in 1905 Starling coined the word hormone, from the Greek for 'to excite'. Takamine and Aldrich isolated adrenaline in 1901. Banting and Best extracted insulin in 1921, and in 1955 Sanger determined insulin's amino-acid sequence, the first protein to be sequenced. In 1965 Chinese scientists achieved the first total synthesis of biologically active crystalline bovine insulin.

1930 年代布特南特、鲁日奇卡测定了性激素结构；1950 年前后肯德尔等合成可的松用于治疗类风湿关节炎。今天重组 DNA 技术生产的人胰岛素、生长激素，以及口服避孕药、糖皮质激素等都是激素化学的成果。植物激素（生长素、赤霉素、乙烯、脱落酸等）调节植物生长发育。

In the 1930s Butenandt and Ružička determined the structures of the sex hormones, and around 1950 Kendall and others made cortisone available for rheumatoid arthritis. Recombinant human insulin and growth hormone, oral contraceptives and glucocorticoids all come from hormone chemistry. Plant hormones such as auxin, gibberellins, ethylene and abscisic acid regulate plant growth and development.