Ominato M, Satoh T, Katz A I
Department of Medicine, University of Chicago Pritzker School of Medicine, Chicago, Illinois 60637, USA.
J Membr Biol. 1996 Aug;152(3):235-43. doi: 10.1007/s002329900101.
To evaluate further the signal transduction mechanisms involved in the short-term modulation of Na-K-ATPase activity in the mammalian kidney, we examined the role of phospholipase C-protein kinase C (PLC-PKC) pathway and of various eicosanoids in this process, using microdissected rat proximal convoluted tubules. Dopamine (DA) and parathyroid hormone (either synthetic PTH1-34 or PTH3-34) inhibited Na-K-ATPase activity in dose-dependent manner; this effect was reproduced by PKC530-558 fragment and blocked by the specific PKC inhibitor calphostin C, as well as by the PLC inhibitors neomycin and U-73122. Pump inhibition by DA, PTH, or arachidonic acid, and by PKC activators phorbol dibutyrate (PDBu) or dioctanoyl glycerol (DiC8) was abolished by ethoxyresorufin, an inhibitor of the cytochrome P450-dependent monooxygenase pathway, but was unaffected by indomethacin or nordihydroguaiaretic acid, inhibitors of the cyclooxygenase and lipoxygenase pathways of the arachidonic acid cascade, respectively. Furthermore, each of the three monooxygenase products tested (20-HETE, 12(R)-HETE, or 11,12-DHT) caused a dose-dependent inhibition of the pump. The effect of DA, PTH, PDBu or DiC8, as well as that of 20-HETE was not altered when sodium entry was blocked with the amiloride analog ethylisopropyl amiloride or increased with nystatin. We conclude that short-term regulation of proximal tubule Na-K-ATPase activity by dopamine and parathyroid hormone occurs via the PLC-PKC signal transduction pathway and is mediated by cytochrome P450-dependent monooxygenase products of arachidonic acid metabolism, which may interact with the pump rather than alter sodium access to it.
为了进一步评估参与哺乳动物肾脏中钠钾ATP酶活性短期调节的信号转导机制，我们使用显微解剖的大鼠近端曲管，研究了磷脂酶C-蛋白激酶C（PLC-PKC）途径以及各种类花生酸在这一过程中的作用。多巴胺（DA）和甲状旁腺激素（合成的PTH1-34或PTH3-34）以剂量依赖的方式抑制钠钾ATP酶活性；PKC530-558片段可重现这种效应，而特异性PKC抑制剂钙泊三醇C以及PLC抑制剂新霉素和U-73122可阻断这种效应。DA、PTH或花生四烯酸，以及PKC激活剂佛波酯（PDBu）或二辛酰甘油（DiC8）对泵的抑制作用，可被细胞色素P450依赖性单加氧酶途径的抑制剂乙氧苯酯消除，但不受分别为花生四烯酸级联反应的环氧化酶途径和脂氧化酶途径抑制剂的吲哚美辛或去甲二氢愈创木酸的影响。此外，所测试的三种单加氧酶产物（20-羟基二十碳四烯酸、12(R)-羟基二十碳四烯酸或11,12-二氢睾酮）中的每一种都引起泵的剂量依赖性抑制。当用氨氯地平类似物乙基异丙基氨氯地平阻断钠内流或用制霉菌素增加钠内流时，DA、PTH、PDBu或DiC8以及20-羟基二十碳四烯酸的作用没有改变。我们得出结论，多巴胺和甲状旁腺激素对近端小管钠钾ATP酶活性的短期调节是通过PLC-PKC信号转导途径发生的，并且由花生四烯酸代谢的细胞色素P450依赖性单加氧酶产物介导，这些产物可能与泵相互作用而不是改变钠进入泵的通道。
