Radioimmunoassay for plasma renin activity
Manjula S. Kumar, Ph.D.
Division of Research
Sharad D. Deodhar, M.D., Ph.D.
Section on Immunopathology
The role of the kidney in the regulation of blood pressure through the secretion of proteolytic enzyme renin was first suggested by Gold-blatt et al1 in 1934. Since then, the interrelations of the different components of the renin-angiotensin system have become known, and it is now clear that renin is not only involved in homeostatic control mechanisms of blood pressure, but also plays an important role in the pathogenesis of certain hypertensive diseases. As a result of more recent observations, it also appears that the renin-angiotensin system is one of the important regulators of aldosterone secretion. Because of this, quantitative laboratory renin determinations of peripheral and renal venous blood have become important in the diagnosis of hypertension. The biological activity of this system involves the enzymatic cleavage of a plasma substrate protein by renin to release a decapeptide angiotensin I, which is converted to octapeptide angiotensin II by the “converting” enzyme during the pulmonary circulation. The latter is not only a highly active pressor agent, but also a major stimulus to aldosterone secretion and, as such, is thought to be the mediator of most of the biologic properties of renin. In the past, quantitative renin determinations were performed only by bioassay procedures. Renin was allowed to interact with its substrate to produce angiotensin II, which then was assayed through its pressor effect in an experimental animal. These bioassays are cumbersome, technically difficult, time-consuming, and relatively insensitive. Also, variations in each experimental animal and in the ability of the technologists to . . .