Pinto-do-O P C, Chibalin A V, Katz A I, Soares-da-Silva P, Bertorello A M
Department of Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
Clin Exp Hypertens. 1997 Jan-Feb;19(1-2):73-86. doi: 10.3109/10641969709080805.
Dopamine (DA) produces a natriuresis attributed in part to inhibition of Na,K-ATPase activity (NKA) in the proximal tubule (PCT), and impairment in this inhibition has been linked to several forms of hypertension in animals. Here we examined whether the intracellular signaling mechanisms involved are the same in the early and late phases of this phenomenon. DA (1 microM) inhibited NKA similarly after 15 min (by 38%) or 180 min (by 36%) incubation, taken to represent short-term (ST) and sustained (Sd) pump regulation, respectively. Calphostin C, a specific inhibitor of protein kinase C (PKC), completely blocked the ST action of DA on NKA, whereas IP20, a specific inhibitor of protein kinase (PKA), had no effect. In contrast, IP20 completely abolished the Sd (180 min) inhibition by DA, whereas calphostin C had only a partial or variable effect. The DA-1 agonist fenoldopam (which does not activate PKC but increases cAMP) alone failed to inhibit the pump at 180 min (as it does also in the short-term in PCT), suggesting that ST inhibition is required for the Sd effect to occur. Furthermore, PTH1-34, a known ST inhibitor of NKA suppressed the pump at 180 min (by 46%), but unlike in the short-term, this effect was completely prevented by IP20. In contrast, PTH3-34, which does not stimulate adenylyl cyclase or activate PKA, caused only a small (19%) and variable Sd inhibition. In conclusion, short-term inhibition of the PCT pump by dopamine is mediated via PKC, whereas the sustained inhibition requires the PKA pathway in addition to the ongoing PKC-mediated effect.
多巴胺（DA）可产生利钠作用，部分原因是其抑制近端小管（PCT）中的钠钾ATP酶活性（NKA），而这种抑制作用的受损与动物的几种高血压形式有关。在此，我们研究了此现象的早期和晚期所涉及的细胞内信号传导机制是否相同。DA（1微摩尔）在孵育15分钟（抑制38%）或180分钟（抑制36%）后对NKA的抑制作用相似，分别代表短期（ST）和持续（Sd）泵调节。钙泊三醇C，一种蛋白激酶C（PKC）的特异性抑制剂，完全阻断了DA对NKA的ST作用，而IP20，一种蛋白激酶（PKA）的特异性抑制剂，则无作用。相反，IP20完全消除了DA的Sd（180分钟）抑制作用，而钙泊三醇C只有部分或可变作用。DA-1激动剂非诺多泮（不激活PKC但增加cAMP）单独在180分钟时未能抑制泵（在PCT的短期也是如此），表明ST抑制是Sd效应发生所必需的。此外，PTH1-34，一种已知的NKA的ST抑制剂，在180分钟时抑制了泵（46%），但与短期不同的是，这种作用被IP20完全阻断。相反，PTH3-34，其不刺激腺苷酸环化酶或激活PKA，仅引起小的（19%）且可变的Sd抑制。总之，多巴胺对PCT泵的短期抑制是通过PKC介导的，而持续抑制除了持续的PKC介导的效应外还需要PKA途径。
