Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
Acta Physiol (Oxf). 2015 Jan;213(1):268-76. doi: 10.1111/apha.12399. Epub 2014 Oct 9.
Renal afferent arterioles are the effector site for autoregulation of glomerular perfusion and filtration. There is synergistic interaction between angiotensin II (ANG II) and adenosine (Ado) in regulating arteriolar contraction; however, the mechanisms are not clear. In this context, this study investigated the contribution of A1 receptor-dependent and independent signalling mechanisms.
Isolated perfused afferent arterioles from transgenic mice (A1 (+/+) and A1 (-/-) ) were used for vascular reactivity studies. Cultured vascular smooth muscle cells (VSMC) were used for phosphorylation studies of signalling proteins that induce arteriolar contraction.
Maximal arteriolar contraction to ANG II was attenuated in A1 (-/-) (22%) compared with A1 (+/+) (40%). Simultaneous incubation with low-dose ado (10(-8) mol L(-1) ) enhanced ANG II-induced contraction in A1 (+/+) (58%), but also in A1 (-/-) (42%). An ado transporter inhibitor (NBTI) abolished this synergistic effect in A1 (-/-) , but not in wild-type mice. Incubation with Ado + ANG II increased p38 phosphorylation in aortic VSMC from both genotypes, but treatment with NBTI only blocked phosphorylation in A1 (-/-) . Combination of ANG II + Ado also increased MLC phosphorylation in A1 (+/+) but not significantly in A1 (-/-) , and NBTI had no effects. In agreement, Ado + ANG II-induced phosphorylation of p38 and MLC in rat pre-glomerular VSMC was not affected by NBTI. However, during pharmacological inhibition of the A1 receptor simultaneous treatment with NBTI reduced phosphorylation of both p38 and MLC to control levels.
Interaction between ANG II and Ado in VSMC normally involves A1 receptor signalling, but this can be compensated by receptor independent actions that phosphorylate p38 MAPK and MLC.
肾入球小动脉是肾小球灌注和滤过自动调节的效应部位。血管紧张素 II（ANG II）和腺苷（Ado）在调节小动脉收缩方面存在协同作用；然而，其机制尚不清楚。在这种情况下，本研究探讨了 A1 受体依赖性和非依赖性信号机制的贡献。
使用来自转基因小鼠（A1（+/+）和 A1（-/-））的分离灌注入球小动脉进行血管反应性研究。培养血管平滑肌细胞（VSMC）用于诱导小动脉收缩的信号蛋白磷酸化研究。
与 A1（+/+）（40%）相比，ANG II 引起的最大入球小动脉收缩在 A1（-/-）（22%）中减弱。同时孵育低剂量 ado（10（-8）mol L（-1））增强了 A1（+/+）（58%）中 ANG II 诱导的收缩，但也增强了 A1（-/-）（42%）中 ANG II 诱导的收缩。ADO 转运蛋白抑制剂（NBTI）在 A1（-/-）中消除了这种协同作用，但在野生型小鼠中没有。ADO+ANG II 孵育增加了来自两种基因型的主动脉 VSMC 中 p38 的磷酸化，但用 NBTI 处理仅阻断了 A1（-/-）中的磷酸化。ANG II+ADO 的组合也增加了 A1（+/+）中 MLC 的磷酸化，但在 A1（-/-）中没有显著增加，并且 NBTI 没有影响。一致地，ADO+ANG II 诱导的大鼠肾小球前 VSMC 中 p38 和 MLC 的磷酸化不受 NBTI 影响。然而，在 A1 受体的药理学抑制期间，同时用 NBTI 处理将两者的磷酸化降低至对照水平。
VSMC 中 ANG II 和 Ado 之间的相互作用通常涉及 A1 受体信号，但这可以通过磷酸化 p38 MAPK 和 MLC 的非受体依赖性作用来补偿。
