Measurement of plasma renin activity.

This chapter describes the measurement of plasma renin activity by calculation of the quantity of angiotensin I that is released in plasma by the action of endogenous enzyme renin on angiotensinogen, the endogenous substrate. Details are given for the generation of angiotensin I from plasma using controlled pH and temperature conditions. The generated angiotensin I is then quantified by a radioimmunoassay using anti-angiotensin I antibody and iodinated angiotensin I as label. Separation of the antibody-bound fraction from the unbound is achieved using dextran-coated charcoal. Additional notes describe critical steps in the assay. The correct procedures for sample handling to overcome the potential problems of cryoactivation of prorenin to renin are described.