Molecular biology of angiotensinogen.

A ngiotensinogen is a moderately abundant / \ 55,000-60,000 Da serum glycoprotein that is -Z \ the precursor to the angiotensin peptides and is the only known naturally occurring renin substrate. It is synthesized by a variety of cells, most prominently hepatocytes, adipocytes, and astrocytes. Most angiotensinogen is extracellular (it is constitutively secreted); thus, there is apparently no way that an organism can orchestrate rapid changes in angiotensinogen concentration. The angiotensinogen gene is regulated by several hormones (e.g., glucocorticoid and estrogen), and angiotensinogen is an acute-phase protein. Angiotensinogen is a member of the serpin gene superfamily, but there is little reason to suppose that this protein is a serine protease inhibitor. The available evidence indicates that angiotensinogen functions solely as an extracellular reservoir of angiotensin peptides. In this article, we attempt a critical review of the literature on the biology of this protein, with an emphasis on recent molecular biological studies. We recommend other recent reviews, for example, those of Tewksbury or Campbell, for alternative views of this subject matter.