[A simple method measuring plasma aldosterone by radioimmunoassay without extraction (author's transl)]

A radioimmunoassay method was developed to measure plasma aldosterone levels. Antibody was produced in rabbits by injecting aldosterone oxime coupled with bovine gamma-globulin once a month. Plasma aldosterone was measured simultaneously by two methods: the direct method without extraction and a method using paper chromatography. 125I-aldosterone was used in the first method and 3H-aldosterone in the second. The antibody had a high specificity adequate to show zero water blank in the first method. Adequate precision, accuracy and sensitivity were obtained in a direct method using 125I-aldosterone. Plasma aldosterone levels were 7.1+/-3.0ng/100ml (Mean +/-SD) in normal subjects and slightly higher after injecting ACTH-Z. The correlative coefficient between the first and the second method was significantly high (r=0.970, P less than 0.001, n=37). Plasma aldosterone was high (34.3+/-14.1ng/100ml, n=7) in primary aldosteronism, slightly high (14.2+/-2.6ng/100ml) in secondary aldosteronism, normal in Cushing's syndrome (10ng/100ml) and low in Addison's disease (1ng/100ml), hypopituitarism (1ng/100ml) and pseudoaldosteronism (2ng/100ml). From these results, it is concluded that the direct method without extraction was a very useful and reliable method for measuring plasma aldosterone. It was superior in simplicity and there is no need to use a liquid scintillation counter.