SUCNR1 and pulmonary arterial hypertension: Therefore, succinate appears to be particularly important in the context of pathological conditions in the pressure-overloaded heart; furthermore, using an aequorin luminescence assay, the half-maximal response succinate concentrations for inducing the activation of human and mouse GPR91 were 56±8 and 28±5 μM, far below the succinate circulating concentration in response to pressure overload in PAH [44,45].