Blankemeyer J T
Fed Proc. 1981 Jul;40(9):2412-6.
Midguts isolated from fifth-instar larvae of the insert Hyalophora cecropia actively transport potassium in the hemolymph to lumen direction. No specific co- or counter-ion is required and other alkali ions are actively transported in the same direction as potassium. No specific inhibitor of K+ active transport has been found although most metabolic inhibitors reduce the net K+ flux, potential difference, and short-circuit current to zero. The site of the epithelial active transport of potassium has been identified by microelectrode measurements of intracellular resistance as the goblet cell, one of the two major cell types in the single-layered midgut. Under certain external conditions, the neighboring columnar cells are added to the goblet cell transport route through intercellular electrical coupling that occurs after application of external depolarizing current. Tracer influx kinetics were used to establish that the fraction of exchangeable K involved in the transport route under open-circuit conditions is small, corresponding to a goblet cell pathway. Under depolarizing current conditions, virtually all of the exchangeable midgut K is involved in the transport route, corresponding to a goblet and columnar cell pathway. These results and others are used to construct a model for rheogenic active transport of potassium in insect midgut.
从大透目天蚕蛾五龄幼虫分离出的中肠能将血淋巴中的钾离子主动转运至肠腔方向。不需要特定的共转运或反向转运离子，其他碱金属离子也与钾离子同向主动转运。虽然大多数代谢抑制剂会使钾离子净通量、电位差和短路电流降至零，但尚未发现钾离子主动转运的特异性抑制剂。通过微电极测量细胞内电阻，已确定钾离子上皮主动转运的部位是杯状细胞，它是单层中肠的两种主要细胞类型之一。在特定的外部条件下，施加外部去极化电流后，相邻的柱状细胞通过细胞间电偶联加入杯状细胞的转运途径。示踪剂流入动力学用于确定在开路条件下参与转运途径的可交换钾的比例很小，这与杯状细胞途径相对应。在去极化电流条件下，几乎所有可交换的中肠钾都参与了转运途径，这与杯状细胞和柱状细胞途径相对应。这些结果及其他结果被用于构建昆虫中肠钾离子生电主动转运的模型。
