Thomas D D, Knoop F C
J Infect Dis. 1983 Mar;147(3):450-9. doi: 10.1093/infdis/147.3.450.
The binding of biologically active 125I-labeled heat-stable enterotoxin (ST) of Escherichia coli with cultured mammalian cells was dose dependent and could be inhibited with low concentrations of unlabeled toxin or by neutralization with specific antiserum. There was positive cooperativity among cell binding sites. A single cultured cell bound approximately 4 X 10(4) molecules of ST; the dissociation constant was 1.33 X 10(-10) M. The specific binding of ST was partially inhibited by Pronase (Sigma Chemical Company, St. Louis, Missouri) and trypsin, but not by lipid- or carbohydrate-specific enzymes, simple sugars, or saccharides. Addition of ST to cultures of rat basophilic leukemia cells resulted in a dose-dependent secretion of histamine. Pharmacologic agents that inhibited calcium uptake or prostaglandin synthesis decreased the amount of histamine released. These data demonstrate the specific binding of ST by cultured cells and support the contention that calcium and prostaglandins may be important in the molecular mechanism(s) whereby ST activates guanylate cyclase.
具有生物活性的大肠杆菌125I标记热稳定肠毒素（ST）与培养的哺乳动物细胞的结合呈剂量依赖性，且可被低浓度的未标记毒素抑制，或被特异性抗血清中和。细胞结合位点之间存在正协同性。单个培养细胞结合约4×10⁴个ST分子；解离常数为1.33×10⁻¹⁰M。ST的特异性结合可被链霉蛋白酶（西格玛化学公司，密苏里州圣路易斯）和胰蛋白酶部分抑制，但不受脂质或碳水化合物特异性酶、单糖或糖类抑制。将ST添加到大鼠嗜碱性白血病细胞培养物中会导致组胺的剂量依赖性分泌。抑制钙摄取或前列腺素合成的药物会减少组胺的释放量。这些数据证明了培养细胞对ST的特异性结合，并支持钙和前列腺素可能在ST激活鸟苷酸环化酶的分子机制中起重要作用这一观点。
