Stretch-Activation of Angiotensin II Type 1a Receptors Contributes to the Myogenic Response of Mouse Mesenteric and Renal Arteries
Rationale: Vascular wall stretch is the major stimulus for the myogenic response of small arteries to pressure. The molecular mechanisms are elusive, but recent findings suggest that G protein-coupled receptors can elicit a stretch response.
Objective: Determine if angiotensin II type 1 receptors (AT1R) in vascular smooth muscle cells (VSMC) exert mechanosensitivity and identify the downstream ion channel mediators of myogenic vasoconstriction.
Methods and Results: We used mice deficient in AT1R signaling molecules and putative ion channel targets, namely AT1R, angiotensinogen, TRPC6 channels or several subtypes of the voltage-gated K+ (Kv7) gene family (KCNQ3, 4 or 5). We identified a mechano-sensing mechanism in isolated mesenteric arteries and in the renal circulation that relies on coupling of the AT1R subtype a (AT1aR) to a Gq/11-protein as a critical event to accomplish the myogenic response. Arterial mechano-activation occurs after pharmacological block of AT1R, and in the absence of angiotensinogen or TRPC6 channels. Activation of AT1aR by osmotically induced membrane stretch suppresses an XE991-sensitive Kv channel current in patch-clamped VSMCs and similar concentrations of XE991 enhance mesenteric and renal myogenic tone. Although XE991-sensitive KCNQ3, 4 and 5 channels are expressed in VSMCs, XE991-sensitive K+ current and myogenic contractions persist in arteries deficient in these channels.
Conclusions: Our results provide definitive evidence that myogenic responses of mouse mesenteric and renal arteries rely on ligand-independent, mechano-activation of AT1aR. The AT1aR signal relies on an ion channel distinct from TRPC6 or KCNQ3, 4 or 5 to enact VSMC activation and elevated vascular resistance.
- Gq proteins
- TRPC channels
- myogenic tone
- Kv7 channels
- angiotensin receptor
- potassium channels
- transgenic mice
- angiotensin II
- Received October 17, 2013.
- Revision received May 15, 2014.
- Accepted May 16, 2014.