Wever Kim E, Masereeuw Rosalinde, Miller David S, Hang Xiao M, Flik Gert
Dept. of Animal Physiology, Institute for Neuroscience Faculty of Science, Radboud Univ. Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
Am J Physiol Renal Physiol. 2007 Jan;292(1):F38-46. doi: 10.1152/ajprenal.00479.2005. Epub 2006 Aug 15.
The kidney of vertebrates plays a key role in excretion of endogenous waste products and xenobiotics. Active secretion in the proximal nephron is at the basis of this excretion, mediated by carrier proteins including multidrug resistance protein 2 (Mrp2). We previously showed that Mrp2 function is reduced by endothelin-1 (ET-1) through a basolateral B-type receptor, nitric oxide (NO), cGMP, and PKC (Notenboom S, Miller DS, Smits P, Russel FGM, Masereeuw R. Am J Physiol Renal Physiol 282: F458-F464, 2002; Notenboom S, Miller DS, Smits P, Russel FG, Masereeuw R. Am J Physiol Renal Physiol 287: F33-F38, 2004). This pathway was rapidly activated by several nephrotoxicants and appeared to be calcium dependent. In the present study, we studied the effect of the calciotropic hormones parathyroid hormone (PTH), PTH-related protein (PTHrP), and stanniocalcin (STC) to interfere with ET-regulated Mrp2 transport. Like ET-1, PTH reduces Mrp2-mediated transport by 40% in killifish renal proximal tubules. When given in combination, an additive effect was seen, which is partially reversed by the PKC inhibitor calphostin C. Recombinant PTHrP shows a comparable inhibitory effect, which is concentration dependent and additive to the inhibition by ET. STC fully reverses PTHrP-inhibited transport as does a guanylyl cyclase inhibitor. Finally, to confirm PTHrP bioactivity in a homologous assay, we performed immunolocalization and transport studies in sea bream kidney tubules. Mrp2 immunoreactivity was observed in approximately 40% of the tubules and is associated with the brush-border and apical plasma membrane of cells. Both proximal tubules and distal (collecting) tubules express the antigen. A highly significant 40% inhibition of Mrp2-mediated transport was observed with PTHrP in sea bream tubules. In conclusion, ET-regulated Mrp2 transport is influenced by calciotropic hormones and involves PKC and cGMP signaling.
脊椎动物的肾脏在排泄内源性废物和外源性物质方面起着关键作用。近端肾单位的主动分泌是这种排泄的基础，由包括多药耐药蛋白2（Mrp2）在内的载体蛋白介导。我们先前表明，内皮素-1（ET-1）通过基底外侧B型受体、一氧化氮（NO）、环鸟苷酸（cGMP）和蛋白激酶C（PKC）降低Mrp2的功能（Notenboom S，Miller DS，Smits P，Russel FGM，Masereeuw R.《美国生理学杂志：肾脏生理学》282：F458-F464，2002；Notenboom S，Miller DS，Smits P，Russel FG，Masereeuw R.《美国生理学杂志：肾脏生理学》287：F33-F38，2004）。该途径被几种肾毒物迅速激活，且似乎依赖于钙。在本研究中，我们研究了钙调节激素甲状旁腺激素（PTH）、甲状旁腺激素相关蛋白（PTHrP）和鲽鱼降钙素（STC）对ET调节的Mrp2转运的干扰作用。与ET-1一样，PTH使鳉鱼肾近端小管中Mrp2介导的转运降低40%。联合使用时，会出现相加效应，PKC抑制剂钙泊三醇C可部分逆转这种效应。重组PTHrP显示出类似的抑制作用，该作用呈浓度依赖性，且与ET的抑制作用相加。STC与鸟苷酸环化酶抑制剂一样，可完全逆转PTHrP抑制的转运。最后，为了在同源试验中确认PTHrP的生物活性，我们在鲷鱼肾小管中进行了免疫定位和转运研究。在大约40%的肾小管中观察到Mrp2免疫反应性，且其与细胞的刷状缘和顶端质膜相关。近端小管和远端（集合）小管均表达该抗原。在鲷鱼肾小管中，PTHrP对Mrp2介导的转运有高达40%的显著抑制作用。总之，ET调节的Mrp2转运受钙调节激素影响，涉及PKC和cGMP信号传导。
