Kansra V, Chen C J, Lokhandwala M F
Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, TX 77204-5511, USA.
Clin Exp Hypertens. 1995 Jul;17(5):837-45. doi: 10.3109/10641969509033638.
We have previously reported that dopamine-1 receptor-mediated activation of phospholipase C is diminished in renal cortical slices of spontaneously hypertensive rats. The present study was carried out to examine the effect of dopamine on protein kinase C (PKC), which is one of the enzymes involved in the signal-transduction pathway leading to dopamine-induced inhibition of Na+/K(+)-ATPase in the renal proximal tubule. Renal proximal tubule suspensions were obtained from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats of 10-12 weeks old. The tubules were incubated with dopamine in the presence or absence of DA-1 receptor antagonist SCH 23390. The PKC activity was measured by using a specific fluorescent peptide substrate (sequence, PKSRTLSVAAK). We found that dopamine produced a concentration-dependent increase in protein kinase C activity in the WKY rats, however, it failed to stimulate PKC activity in the SHR. Peak stimulation of 3.828 +/- 0.35 (ng/micrograms) protein in the WKY rats was observed at dopamine concentration of 1 microM, which was blocked in a concentration-dependent manner by SCH 23390 (0.25 microM). These results provide evidence that dopamine directly stimulates PKC activity via activation of DA-1 receptors in WKY rats. Furthermore, we discovered that dopamine fails to stimulate PKC activity in the SHR. This phenomenon may be responsible for the failure of dopamine to inhibit Na+/K(+)-ATPase activity in the hypertensive animals.
我们之前曾报道，在自发性高血压大鼠的肾皮质切片中，多巴胺-1受体介导的磷脂酶C激活作用减弱。本研究旨在探讨多巴胺对蛋白激酶C（PKC）的影响，PKC是参与多巴胺诱导肾近端小管中钠钾ATP酶抑制作用的信号转导途径的酶之一。从10 - 12周龄的自发性高血压大鼠（SHR）和Wistar - Kyoto（WKY）大鼠获取肾近端小管悬液。在存在或不存在DA - 1受体拮抗剂SCH 23390的情况下，将小管与多巴胺一起孵育。通过使用特定的荧光肽底物（序列，PKSRTLSVAAK）测量PKC活性。我们发现，多巴胺使WKY大鼠的蛋白激酶C活性呈浓度依赖性增加，然而，它未能刺激SHR中的PKC活性。在多巴胺浓度为1 microM时，观察到WKY大鼠中蛋白激酶C活性的峰值刺激为3.828±0.35（ng/微克），这被SCH 23390（0.25 microM）以浓度依赖性方式阻断。这些结果证明多巴胺通过激活WKY大鼠中的DA - 1受体直接刺激PKC活性。此外，我们发现多巴胺未能刺激SHR中的PKC活性。这种现象可能是多巴胺无法抑制高血压动物中钠钾ATP酶活性的原因。
