Vassallo D V, Songu-Mize E, Rossoni L V, Amaral S M
Departamento de Ciências Fisiológicas, Universidade Federal do Espírito Santo, Vitória, Brasil.
Braz J Med Biol Res. 1997 Apr;30(4):545-52. doi: 10.1590/s0100-879x1997000400016.
Ouabain is an endogenous substance occurring in the plasma in the nanomolar range, that has been proposed to increase vascular resistance and induce hypertension. This substance acts on the alpha-subunit of Na+,K(+)-ATPase inhibiting the Na(+)-pump activity. In the vascular smooth muscle this effect leads to intracellular Na+ accumulation that reduces the activity of the Na+/Ca2+ exchanger and to an increased vascular tone. It was also suggested that circulating ouabain, even in the nanomolar range, sensitizes the vascular smooth muscle to vasopressor substances. We tested the latter hypothesis by studying the effects of ouabain in the micromolar and nanomolar range on phenylephrine (PE)-evoked pressor responses. The experiments were performed in normotensive and hypertensive rats in vivo, under anesthesia, and in perfused rat tail vascular beds. The results showed that ouabain pretreatment increased the vasopressor responses to PE in vitro and in vivo. This sensitization after ouabain treatment was also observed in hypertensive animals which presented an enhanced vasopressor response to PE in comparison to normotensive animals. It is suggested that ouabain at nanomolar concentrations can sensitize vascular smooth muscle to vasopressor stimuli possibly contributing to increased tone in hypertension.
哇巴因是一种内源性物质，在血浆中的浓度处于纳摩尔范围，有人提出它会增加血管阻力并诱发高血压。这种物质作用于Na⁺,K⁺-ATP酶的α亚基，抑制Na⁺泵的活性。在血管平滑肌中，这种作用会导致细胞内Na⁺积累，从而降低Na⁺/Ca²⁺交换体的活性，并使血管张力增加。也有人提出，即使是纳摩尔范围内的循环哇巴因，也会使血管平滑肌对血管升压物质敏感。我们通过研究微摩尔和纳摩尔范围内的哇巴因对去氧肾上腺素（PE）诱发的升压反应的影响，来验证后一种假设。实验在麻醉状态下的正常血压和高血压大鼠体内以及灌注的大鼠尾血管床中进行。结果表明，哇巴因预处理可增强体外和体内对PE的升压反应。在高血压动物中也观察到哇巴因处理后的这种敏化作用，与正常血压动物相比，高血压动物对PE的升压反应增强。有人提出，纳摩尔浓度的哇巴因可使血管平滑肌对血管升压刺激敏感，这可能导致高血压时血管张力增加。
