Measurement of plasma renin activity.

Measurement of angiotensin 1, released in plasma by the action of endogenous enzyme renin on endogenous substrate, angiotensinogen is described. Details are given for the generation of angiotensin 1 from plasma using controlled conditions of pH and temperature. A radioimmunoassay to quantify the generated material is then described using anti-angiotensin 1 antibody and iodinated angiotensin 1 as label. Separation of the antibody-bound fraction from the free is achieved using dextran-coated charcoal. Problems of cryoactivation of prorenin and the labile nature of angiotensin 1 are highlighted. Additional notes describe steps in the assay that are critical.