1. A method for extraction, partial purification and radioimmunoassay of angiotensin II in tissues and application of the method to the kidneys of sodium-deficient rats are described.
2. Angiotensin in acid—ethanol extracts of kidney were adsorbed on to a cation-exchange resin, eluted and further purified with an immobilized angiotensin II antiserum, before radioimmunoassay.
3. Thin-layer chromatography was used, in some experiments, to separate fmol amounts of angiotensin II from its immunoreactive peptide fragments before radioimmunoassay.
4. Angiotensin II-immunoreactive material isolated from rat kidney resembled angiotensin II in many of its physicochemical properties and chromatographic mobility.
5. The concentration of immunoreactive material in kidney greatly exceeded that which could be accounted for by trapped blood and suggests that the peptide may have a local role in the organ.