HIGHLY SENSITIVE MICROASSAY FOR ALDOSTERONE IN UNEXTRACTED PLASMA - COMPARISON WITH 2 OTHER METHODS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 104  (5) , 789-796
Abstract
A direct radioimmunoassay for aldosterone in unextracted plasma [from humans] was developed using a highly sensitive and specific antiserum and 125I-labeled aldosterone. This new method was compared with the previously used assay based on methylene chloride extraction and column chromatography and with a micromethod utilizing methylene chloride extraction alone. Concentrations of 2 pg/ml aldosterone can be measured in 25 .mu.l plasma. The within-assay coefficient of variation ranged between 4.0% and 5.3% over a 6-fold range of aldosterone concentrations and the between-assay coefficient of variation ranged between 5.0% and 9.4% over a 10-fold range. The correlation coefficients among the 3 methods varied between 0.97 and 0.99 and results were virtually identical between the new direct and the standard chromatography methods. Normal values on unrestricted salt intake were 68 .+-. 28 pg/ml (n = 30, mean .+-. SD) in seated humans. This is an extremely simple, truly direct microradioimmunoassay for plasma aldosterone that is accurate over a wide range of plasma concentrations, is exquisitely sensitive and provides results identical to those obtained with established methods.