Giannella R A, Luttrell M, Thompson M
Am J Physiol. 1983 Oct;245(4):G492-8. doi: 10.1152/ajpgi.1983.245.4.G492.
This study was performed to determine whether receptors for Escherichia coli heat-stable enterotoxin (ST) exist on intestinal epithelial cells. Binding sites for 125I-ST were found on rat jejunal and ileal villus cells. Binding was rapid, reversible, linear with cell number, saturable, and temperature dependent. Significant degradation of 125I-ST occurred when incubated with cells at 37 degrees C but not at 25 degrees C. Binding was specific to ST since binding of 125I-ST was competitively inhibited by increasing concentrations of human or porcine ST but not by E. coli heat-labile, cholera, or staphylococcal enterotoxins. Addition of excess unlabeled ST to cells preincubated with 125I-ST resulted in dissociation of much but not all of the bound 125I-ST. Binding of 125I-ST to jejunal and ileal cells occurs with two affinities, and this is due to the phenomenon of negative cooperativity. The potency of ST for inhibiting the binding of 125I-ST was identical to the potency of ST in stimulating cGMP production. These data support the existence of receptors for ST on intestinal cells, and these receptors may be involved in the action of ST.
本研究旨在确定肠道上皮细胞上是否存在大肠杆菌热稳定肠毒素（ST）的受体。在大鼠空肠和回肠绒毛细胞上发现了125I-ST的结合位点。结合迅速、可逆、与细胞数量呈线性关系、可饱和且依赖温度。当在37℃与细胞一起孵育时，125I-ST会发生显著降解，但在25℃时不会。结合对ST具有特异性，因为125I-ST的结合会被浓度增加的人或猪ST竞争性抑制，但不会被大肠杆菌不耐热肠毒素、霍乱毒素或葡萄球菌肠毒素抑制。向预先用125I-ST孵育的细胞中加入过量未标记的ST会导致大部分但并非全部结合的125I-ST解离。125I-ST与空肠和回肠细胞的结合具有两种亲和力，这是由于负协同效应现象。ST抑制125I-ST结合的效力与ST刺激cGMP产生的效力相同。这些数据支持肠道细胞上存在ST受体，并且这些受体可能参与ST的作用。
