Kawamoto F, Shozawa A, Kumada N, Kojima K
Department of Medical Zoology, Nagoya University School of Medicine, Japan.
Parasitol Res. 1989;75(5):368-74. doi: 10.1007/BF00931132.
The triggering action of physiological saline in the miracidial transformation of Schistosoma mansoni was analyzed using various agents affecting cAMP- and Ca2+-dependent pathways. Potent activators of adenylate cyclase, such as forskolin and serotonin, strongly inhibited the transformation provoked by saline in RPMI-1640. These inhibitory actions were diminished by the combined administration of phosphodiesterase activators such as ammonium salts or imidazole. Furthermore, the exposure of miracidia to ammonium salts or imidazole in dechlorinated tap water "mimicked" the transformation, i.e., the cessation, of swimming and then shedding of epithelial plates. This mimic transformation was also inhibited by serotonin or forskolin. In contrast, treatment of miracidia with Ca2+ antagonists such as TMB-8 (an inhibitor of Ca2+ release), nicardipine (a Ca2+ channel blocker), or W-7 (a calmodulin inhibitor) in tap water produced severe vesiculation on their body surfaces and resulted in death. However, these toxic effects were abolished by a combined administration of these Ca2+ antagonists with saline or NH4Cl, and the transformation was reestablished except with W-7 treatment. W-7 strongly inhibited the triggering action of saline and NH4Cl and the worms swam slowly, whereas W-5, an inactive analogue of W-7, had no inhibitory effect on the transformation. These results suggest that the initiation of micracidial transformation to young sporocysts may be synergistically regulated by cAMP and Ca2+ and that a decrease in cAMP levels and an increase in Ca2+ mobilization may be provoked in worms transformed by saline, ammonium salts, or imidazole.
利用各种影响环磷酸腺苷（cAMP）和钙离子（Ca2+）依赖途径的试剂，分析了生理盐水在曼氏血吸虫毛蚴转化过程中的触发作用。腺苷酸环化酶的强效激活剂，如福斯可林和血清素，强烈抑制了RPMI-1640培养基中生理盐水引发的转化。磷酸二酯酶激活剂如铵盐或咪唑的联合使用可减弱这些抑制作用。此外，将毛蚴暴露于脱氯自来水中的铵盐或咪唑会“模拟”转化过程，即游泳停止，然后上皮板脱落。这种模拟转化也受到血清素或福斯可林的抑制。相比之下，在自来水中用Ca2+拮抗剂如TMB-8（一种Ca2+释放抑制剂）、尼卡地平（一种Ca2+通道阻滞剂）或W-7（一种钙调蛋白抑制剂）处理毛蚴，会使其体表产生严重的水泡并导致死亡。然而，将这些Ca2+拮抗剂与生理盐水或氯化铵联合使用可消除这些毒性作用，除了W-7处理外，转化得以重新建立。W-7强烈抑制生理盐水和氯化铵的触发作用， worms游动缓慢，而W-7的无活性类似物W-5对转化没有抑制作用。这些结果表明，毛蚴向年轻孢蚴的转化起始可能由cAMP和Ca2+协同调节，并且在经生理盐水、铵盐或咪唑转化的虫体中，可能会引发cAMP水平降低和Ca2+动员增加。
