Baines R J, Brown C, Ng L L, Boarder M R
Department of Cell Physiology and Pharmacology, School of Medicine, University of Leicester, UK.
Hypertension. 1996 Nov;28(5):772-8. doi: 10.1161/01.hyp.28.5.772.
Vascular smooth muscle cells of the spontaneously hypertensive rat (SHR) are known to show increased responsiveness to angiotensin II (Ang II) compared with cells of normotensive control Wistar-Kyoto rats (WKY). We investigated the hypothesis that differential levels of cGMP lead to the different responsiveness of the cells, using vascular smooth muscle cells in culture. cGMP levels in extracts of SHR-derived cells were lower than those of WKY-derived cells. This was true for both unstimulated cells and cells treated with equal concentrations of either sodium nitroprusside or S-nitroso-N-acetylpenicillamine. Stimulation of cells with Ang II did not affect levels of cGMP but increased levels of inositol 1, 4, 5-trisphosphate (IP3) and Ca2+, which were greater in SHR- than in WKY-derived cells. When SHR and WKY cells were preincubated with different concentrations of S-nitroso-N-acetylpenicillamine to generate similar cGMP levels in each cell type, the subsequent IP3 response to Ang II was the same in the two cell types. To reduce any influence of cGMP on responses, we permeabilized the cells with alpha-toxin. Stimulation of alpha-toxin-permeabilized the cells with high Ca2+ revealed an IP3 response in SHR- but not WKY-derived cells. Similarly, permeabilized SHR cells responded to Ang II but WKY cells did not. However, GTP and GTP gamma S elevated IP3 in both cell types. Taken together, these results indicate that the low response of WKY cells can be accounted for by the inhibitory influence of cGMP. However, when this inhibition is removed by permeabilization, further differences between the cells are revealed that will contribute to the elevated SHR response.
与正常血压的对照Wistar-Kyoto大鼠（WKY）的细胞相比，自发性高血压大鼠（SHR）的血管平滑肌细胞对血管紧张素II（Ang II）的反应性增加。我们使用培养的血管平滑肌细胞研究了cGMP水平差异导致细胞反应性不同的假说。SHR来源细胞提取物中的cGMP水平低于WKY来源细胞。无论是未刺激的细胞还是用等量硝普钠或S-亚硝基-N-乙酰青霉胺处理的细胞都是如此。用Ang II刺激细胞不会影响cGMP水平，但会增加肌醇1,4,5-三磷酸（IP3）和Ca2+的水平，SHR来源细胞中的这些水平高于WKY来源细胞。当SHR和WKY细胞用不同浓度的S-亚硝基-N-乙酰青霉胺预孵育以在每种细胞类型中产生相似的cGMP水平时，随后两种细胞类型对Ang II的IP3反应相同。为了减少cGMP对反应的任何影响，我们用α-毒素使细胞通透。用高Ca2+刺激α-毒素通透的细胞显示SHR来源细胞中有IP3反应，而WKY来源细胞中没有。同样，通透的SHR细胞对Ang II有反应，而WKY细胞没有。然而，GTP和GTPγS在两种细胞类型中均升高了IP3。综上所述，这些结果表明WKY细胞的低反应性可由cGMP的抑制作用来解释。然而，当通过通透作用去除这种抑制时，细胞之间进一步的差异就会显现出来，这将导致SHR反应增强。
