Frohman L A, Szabo M, Berelowitz M, Stachura M E
J Clin Invest. 1980 Jan;65(1):43-54. doi: 10.1172/JCI109658.
Growth hormone (GH)-releasing activity has been detected in extracts of carcinoid and pancreatic islet tumors from three patients with GH-secreting pituitary tumors and acromegaly. Bioactivity was demonstrated in 2 N acetic acid extracts of the tumors using dispersed rat adenohypophyseal cells in primary monolayer culture and a rat anterior pituitary perifusion system. The GH-releasing effect was dose responsive and the greatest activity was present in the pancreatic islet tumor. Small amounts of activity were also found in two other tumors (carcinoid and small cell carcinoma of lung) unassociated with GH hypersecretion. Each of the tumors contained somatostatin-like immunoreactivity but the levels did not correlate with the net biologic expression of the tumor. Sephadex G-75 gel filtration indicated the GH-releasing activity to have an apparent molecular size of slightly greater than 6,000 daltons. The GH-releasing activity was adsorbed onto DEAE-cellulose at neutral pH and low ionic strength, from which it could be eluted by increasing ionic strength. The GH-releasing activity was further purified by high pressure liquid chromatography using an acetonitrile gradient on a cyanopropyl column to yield a preparation that was active at 40 ng protein/ml. Partially purified GH-releasing activity, from which most of the bioactive somatostatin had been removed, increased GH release by pituitary monolayer cultures to five times base line. Enzymatic hydrolysis studies revealed that the GH-releasing activity was resistant to carboxypeptidase, leucine-aminopeptidase, and pyroglutamate-amino-peptidase but was destroyed by trypsin and chymotrypsin, indicating that internal lysine and/or arginine and aromatic amino acid residues are required for biologic activity and that the NH2-terminus and CO9H-terminus are either blocked or not essential. The results provide an explanation for the presence of GH-secreting tumors in some patients with the multiple endocrine neoplasia syndrome, type I, and warrant the addition of GH-releasing activity to the growing list of hormones secreted by tumors of amine precursor uptake and decarboxylation cell types.
在3例患有生长激素分泌型垂体瘤及肢端肥大症患者的类癌和胰岛肿瘤提取物中检测到了生长激素（GH）释放活性。利用原代单层培养的分散大鼠腺垂体细胞和大鼠垂体前叶灌流系统，在肿瘤的2N乙酸提取物中证实了生物活性。GH释放效应呈剂量依赖性，且胰岛肿瘤中的活性最强。在另外两种与GH分泌过多无关的肿瘤（类癌和肺小细胞癌）中也发现了少量活性。每种肿瘤均含有生长抑素样免疫反应性，但水平与肿瘤的净生物学表达不相关。Sephadex G - 75凝胶过滤显示，GH释放活性的表观分子大小略大于6000道尔顿。GH释放活性在中性pH和低离子强度下吸附到DEAE - 纤维素上，通过增加离子强度可将其洗脱。使用乙腈梯度在氰丙基柱上进行高压液相色谱进一步纯化GH释放活性，得到一种在40 ng蛋白质/ml时具有活性的制剂。大部分生物活性生长抑素已被去除的部分纯化GH释放活性，使垂体单层培养物中的GH释放增加至基线的5倍。酶解研究表明，GH释放活性对羧肽酶、亮氨酸氨肽酶和焦谷氨酸氨肽酶有抗性，但被胰蛋白酶和糜蛋白酶破坏，这表明生物活性需要内部赖氨酸和/或精氨酸以及芳香族氨基酸残基，且NH2末端和COOH末端要么被封闭，要么不是必需的。这些结果为I型多发性内分泌肿瘤综合征某些患者中存在GH分泌肿瘤提供了解释，并且有必要将GH释放活性添加到由胺前体摄取和脱羧细胞类型肿瘤分泌的不断增加的激素列表中。
