A DOUBLE ISOTOPE DERIVATIVE METHOD FOR THE DETERMINATION OF ALDOSTERONE IN PERIPHERAL PLASMA

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Abstract
The details of a method for the determination of aldosterone at the level of 1 ng or more are described. A combination of the isotope derivative principle and the isotope dilution principle, using 35S and 131I labelled piodobenzenesulfonic acid anhydride (pipsan) as the labelled reagents, has been employed. A quantitative or almost quantitative and reproducible esterification of the 21-hydroxyl group of aldosterone and an 80% recovery of the steroid added to plasma can be achieved by the procedure described. The blank value has been determined by the analysis of epripheral plasma of adrenalectomized dogs and was found to be indistinguishable from zero and therefore less than 3 ng per 100 ml of plasma. In salt depleted anaesthetized dogs the aldosterone level was 20–30 ng per 100 ml. The concentration increased considerably during adrenalectomy and decreased with a »half life« of 20–30 minutes from the time this was completed.