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Background Hypertension is the major risk factor for cardiovascular disease, the most common cause of death worldwide. Resistance arteries are capable of adapting their diameter independently in response to pressure and flow‐associated shear stress. Ryanodine receptors (RyRs) are major Ca2+‐release channels in the sarcoplasmic reticulum membrane of myocytes that contribute to the regulation of contractility. Vascular smooth muscle cells exhibit 3 different RyR isoforms (RyR1, RyR2, and RyR3), but the impact of individual RyR isoforms on adaptive vascular responses is largely unknown. Herein, we generated tamoxifen‐inducible smooth muscle cell–specific RyR2‐deficient mice and tested the hypothesis that vascular smooth muscle cell RyR2s play a specific role in elementary Ca2+ signaling and adaptive vascular responses to vascular pressure and/or flow. Methods and Results Targeted deletion of the Ryr2 gene resulted in a complete loss of sarcoplasmic reticulum–mediated Ca2+‐release events and associated Ca2+‐activated, large‐conductance K+ channel currents in peripheral arteries, leading to increased myogenic tone and systemic blood pressure. In the absence of RyR2, the pulmonary artery pressure response to sustained hypoxia was enhanced, but flow‐dependent effects, including blood flow recovery in ischemic hind limbs, were unaffected. Conclusions Our results establish that RyR2‐mediated Ca2+‐release events in VSCMs specifically regulate myogenic tone (systemic circulation) and arterial adaptation in response to changes in pressure (hypoxic lung model), but not flow. They further suggest that vascular smooth muscle cell–expressed RyR2 deserves scrutiny as a therapeutic target for the treatment of vascular responses in hypertension and chronic vascular diseases.

Background Blood pressure and tissue perfusion are controlled in part by the level of intrinsic (myogenic) arterial tone. However, many of the molecular determinants of this response are unknown. We previously found that mice with targeted disruption of the gene encoding the angiotensin II type 1a receptor (AT1AR) (Agtr1a), the major murine angiotensin II type 1 receptor (AT1R) isoform, showed reduced myogenic tone; however, uncontrolled genetic events (in this case, gene ablation) can lead to phenotypes that are difficult or impossible to interpret. Methods and Results We tested the mechanosensitive function of AT1R using tamoxifen‐inducible smooth muscle‐specific AT1aR knockout (smooth muscle‐Agtr1a−/−) mice and studied downstream signaling cascades mediated by Gq/11 and/or β‐arrestins. FR900359, Sar1Ile4Ile8‐angiotensin II (SII), TRV120027 and TRV120055 were used as selective Gq/11 inhibitor and biased agonists to activate noncanonical β‐arrestin and canonical Gq/11 signaling of the AT1R, respectively. Myogenic and Ang II‐induced constrictions were diminished in the perfused renal vasculature, mesenteric and cerebral arteries of smooth muscle‐Agtr1a−/− mice. Similar effects were observed in arteries of global mutant Agtr1a−/− but not Agtr1b−/− mice. FR900359 decreased myogenic tone and angiotensin II‐induced constrictions whereas selective biased targeting of AT1R‐β‐arrestin signaling pathways had no effects. Conclusions This study demonstrates that myogenic arterial constriction requires Gq/11‐dependent signaling pathways of mechanoactivated AT1R but not G protein‐independent, noncanonical pathways in smooth muscle cells.