Lee Yun Jung, Park Soo Hyun, Jeung Tae Oh, Kim Kee Won, Lee Jang Hern, Han Ho Jae
Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
J Cell Physiol. 2005 Oct;205(1):68-76. doi: 10.1002/jcp.20367.
ATP has been known to act as an extracellular signal and to be involved in various functions of kidney. Renal proximal tubular reabsorption of phosphate (Pi) contributes to the maintenance of phosphate homeostasis, which is regulated by Na+/Pi cotransporter. However, the effects of ATP on Na+/Pi cotransporters were not elucidated in proximal tubule cells (PTCs). Thus, the effects of ATP on Na+/Pi cotransporter and its related signal pathways are examined in the primary cultured renal PTCs. In the present study, ATP inhibited Pi uptake in a time (> 1 h) and dose (>10(-6)M) dependent manner. ATP-induced inhibition of Pi uptake was correlated with the decrease of type II Na+/Pi cotransporter mRNA. ATP-induced inhibition of Pi uptake may be mediated by P2Y receptor activation, since suramin (non-specific P2 receptor antagonist) and RB-2 (P2Y receptor antagonist) blocked it. ATP-induced inhibition of Pi uptake was blocked by neomycin, U73122 (phospholipase C (PLC) inhibitors), bisindolylmaleimide I, H-7, and staurosporine (protein kinase C (PKC) inhibitors), suggesting the role of PLC/PKC pathway. ATP also increased inositol phosphates (IPs) formation and induced PKC translocation from cytosolic fraction to membrane fraction. In addition, ATP-induced inhibition of Pi uptake was blocked by SB 203580 [a p38 mitogen activated protein kinase (MAPK) inhibitor], but not by PD 98059 (a p44/42 MAPK inhibitor). Indeed, ATP induced phosphorylation of p38 MAPK, which was not blocked by PKC inhibitor. In conclusion, ATP inhibited Pi uptake via PLC/PKC as well as p38 MAPK in renal PTCs.
已知三磷酸腺苷（ATP）可作为一种细胞外信号，并参与肾脏的多种功能。肾脏近端小管对磷酸盐（Pi）的重吸收有助于维持磷酸盐稳态，而这一过程由钠/磷酸盐共转运体调节。然而，ATP对近端小管细胞（PTCs）中钠/磷酸盐共转运体的影响尚未阐明。因此，在原代培养的肾脏PTCs中研究了ATP对钠/磷酸盐共转运体及其相关信号通路的影响。在本研究中，ATP以时间（>1小时）和剂量（>10（-6）M）依赖性方式抑制Pi摄取。ATP诱导的Pi摄取抑制与II型钠/磷酸盐共转运体mRNA的减少相关。ATP诱导的Pi摄取抑制可能由P2Y受体激活介导，因为苏拉明（非特异性P2受体拮抗剂）和RB-2（P2Y受体拮抗剂）可阻断该抑制作用。ATP诱导的Pi摄取抑制被新霉素、U73122（磷脂酶C（PLC）抑制剂）、双吲哚马来酰亚胺I、H-7和星形孢菌素（蛋白激酶C（PKC）抑制剂）阻断，提示PLC/PKC途径的作用。ATP还增加了肌醇磷酸（IPs）的形成，并诱导PKC从胞质组分转位至膜组分。此外，ATP诱导的Pi摄取抑制被SB 203580 [一种p38丝裂原活化蛋白激酶（MAPK）抑制剂]阻断，但未被PD 98059（一种p44/42 MAPK抑制剂）阻断。实际上，ATP诱导了p38 MAPK的磷酸化，而PKC抑制剂并未阻断该磷酸化。总之，ATP通过PLC/PKC以及p38 MAPK抑制肾脏PTCs中的Pi摄取。
