APLN and Hypertension: The peripheral apelinergic system appears to be down-regulated in hypertensive disease, with changes in the levels of both immunoreactive (ir)-APJ and/or apln/apelin in human (Sonmez et al., 2010; Chandra et al., 2011; Zhu et al., 2013) and some rodent hypertension models (Zhang et al., 2006).