We investigated the relationships between vascular endothelium and parathyroid function. Blood pressure (BP), circulating endothelins (ETs) and atrial natriuretic peptide (ANP), and BP responses to parathyroid hormone (PTH) and NG-nitro-L-arginine methyl ester (L-NAME) were measured in parathyroidectomized (PTx), PTx and fed a Ca2+ enriched diet (PTx-HCa) and sham SHR.22 weeks after surgery, BP was significantly decreased in PTx and PTx-HCa, plasma ETs levels were increased, whereas ANP levels were decreased. In anesthetized rats, BP increase induced by L-NAME was greater in PTx-HCa than in sham group, indicating increased endogenous nitric oxide release in hypoparathyroid rats. The hypotensive response to PTH remained unchanged. These data demonstrate that endothelium is activated in long-term hypoparathyroid SHR, reflecting an adaptative response to decreased BP.