Hormones of the kidney

Abstract

The kidney plays an essential role in the maintenance of life in higher organisms, not only through regulating the blood pressure and body fluid homeostasis and clearing the wastes, but also by acting as a major endocrine organ. The kidney secretes (1) renin, a key enzyme of the renin-angiotensin system (RAS) that leads to the production of a potent pressor hormone angiotensin, and produces the following hormones and humoral factors: (2) kallikreins, a group of serine proteases that act on blood proteins to produce a vasorelaxing peptide bradykinin; (3) erythropoietin (EPO), a peptide hormone essential for red blood cell (RBC) formation by the bone marrow; and (4) 1,25-(OH)2 vitamin D3, the active form of vitamin D essential for calcium homeostasis, which is produced by the proximal tubule cells via the enzyme 1α-hydroxylase. © 2005 Humana Press Inc.