AGT(25-31) (Angiotensin-(1-7)), a heptapeptide proteolytic product of Angiotensinogen, binds MAS1 (inferred from mouse homologs in Santos et al. 2003). MAS1 is a G protein coupled receptor that has been described to signal via Galpha(i) (Burghi et al. 2019). MAS1 may also constitutively signal via Galpha(q)/(11) (Canals et al. 2006). Signaling by mouse Agt(29-35):Mas1 causes phosphorylation of NOS3 (eNOS) and production of nitric oxide that presumably results in vasodilation (Oliveira Sampaio et al. 2007, Montezano et al. 2025). AGT(25-31) and MAS1 are part of the counter-regulatory arm of the renin-angiotensin system and reduce hypertension and inflammation (reviewed in Santos et al. 2018, Bader et al. 2024, Proença et al. 2024).