A radioimmunoassay for aldosterone in human peripheral plasma including a comparison of alternate techniques.

Abstract

An accurate and relatively simple radioimmunoassay method for the measurement of aldosterone in human plasma is described. One ml or less plasma with 3H aldosterone (2 pg) is extracted with dichloromethane. Two alternative purification steps are described, either a standard paper chromatography (B5) or a more rapid Sephadex LH-20 column (60 × 1 cm) in the system dichloromethane: methanol 98:2 provides adequate purification for analysis. The assay uses either an antibody of high specificity generated against aldosterone-18, 21-disuccinate, or the 3-oxime coupled to bovine albumin. The samples, or standards, are incubated for 1–2 hours at 5° C with dilute antibody and 3H aldostercne. Separation of bound from free aldosterone is affected with activated and coarse-graded Florisil. This one-day method, using the disuccinate antibody and the LH-20 column, is associated with blank values difficult to distinguish from zero (< 6 pg). Aldosterone values from adrenalectomized subjects or duplicate samples after cort...