NOS1 and hypertensive heart disease: This review discusses the histomorphometric changes in capillary density, fibrosis, and mast cells in the hypertensive myocardium and delves into the roles of key regulatory systems, including the apelinergic system, vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathways, and nitric oxide (NO)/nitric oxide synthase (NOS) signaling in the pathogenesis of hypertensive heart disease (HHD).