Angiotensin II, Vasopressin, and Collagen-IV Expression in the Subfornical Organ in a Case of Syndrome of Inappropriate ADH

The syndrome of inappropriate antidiuretic hormone (SIADH) is a disease characterized by hyponatremia and hyperosmolarity of urine where vasopressin and angiotensin II are implicated in the alteration of salt water balance and cardiovascular and blood pressure regulation. The aim of this study is to analyse the expression of substances related with cardiovascular and salt water regulation in the subfornical organ in a case of SIADH. Two brains, one taken from a 66-year-old man with SIADH and the other from a 63-year-old man without SIADH, were used. Immunohistochemical study was performed using anti-angiotensin II, anti-vasopressin, and anti-collagen-VI as primary antibodies. Angiotensin and vasopressin immunoreaction were found in neurons, in perivascular spaces, and in the ependymal layer in the subfornical organ in both cases. However, in the SIADH case, the angiotensin II and collagen-IV expression in the SFO were different suggesting this organ’s possible participation in the physiopathology of SIADH.