Hansch E, Forgo J, Murer H, Biber J
Institute of Physiology, University of Zürich-Irchel, Switzerland.
Pflugers Arch. 1993 Feb;422(5):516-22. doi: 10.1007/BF00375080.
The role of microtubules and actin microfilaments in adaptive changes of the apical Na-dependent transport of phosphate (Pi) was investigated in opossum kidney (OK) cells. Up-regulation of Na/Pi cotransport was achieved by incubating OK cells in a medium containing 0.1 mM Pi; down-regulation of Na/Pi cotransport was provoked by refeeding adapted cells with 2 mM Pi. Up-regulation of Na/Pi cotransport was found to be inhibited by approximately 50% after a pretreatment of the cells with the microtubule disrupting agents nocodozole and colchicine; indirect immunofluorescence indicated complete depolymerization of the microtubular network. No inhibition of the adaptive response was observed after treatment of the cells with cytochalasin B to depolymerize actin microfilaments. In adapted cells, depolymerization of microtubules by nocodozole led to a reversibility of Na/Pi cotransport similar to that observed after refeeding adapted cells with 2 mM Pi. No effects of the microtubule disrupting drugs were observed on Na/L-glutamic acid transport. Depolymerization of microtubules did not prevent parathyroid-hormone-mediated inhibition of Na/Pi cotransport. It is concluded that microtubules are (at least in part) involved in the correct insertion of newly synthesized apical Na/Pi cotransport systems and that microtubules are not involved in the internalization of Na/Pi cotransport systems.
在负鼠肾（OK）细胞中研究了微管和肌动蛋白微丝在顶端钠依赖性磷酸盐（Pi）转运适应性变化中的作用。通过将OK细胞置于含0.1 mM Pi的培养基中孵育来实现钠/磷酸盐共转运的上调；用2 mM Pi重新喂养适应的细胞可引发钠/磷酸盐共转运的下调。在用微管破坏剂诺考达唑和秋水仙碱对细胞进行预处理后，发现钠/磷酸盐共转运的上调被抑制了约50%；间接免疫荧光显示微管网络完全解聚。在用细胞松弛素B处理细胞以使肌动蛋白微丝解聚后，未观察到对适应性反应的抑制。在适应的细胞中，诺考达唑使微管解聚导致钠/磷酸盐共转运的可逆性，类似于用2 mM Pi重新喂养适应的细胞后观察到的情况。未观察到微管破坏药物对钠/L-谷氨酸转运有影响。微管解聚并未阻止甲状旁腺激素介导的钠/磷酸盐共转运抑制。得出的结论是，微管（至少部分）参与新合成的顶端钠/磷酸盐共转运系统的正确插入，并且微管不参与钠/磷酸盐共转运系统的内化。
