PLASMA ALDOSTERONE DETERMINATION WITH 35S-p-TOLUENE-SULPHONIC ANHYDRIDE

ABSTRACT The double isotope derivative method for plasma aldosterone, (Bojesen & Thuneberg 1967), has been applied to human peripheral plasma. 35S-p-toluene-sulphonic anhydride was used as the labelled reagent (100–150 mCi/mEq.) and 3H-aldosterone (30 Ci/mm; 0.05 ng added to each sample) as indicator. The initial derivative (aldosterone-21-35S-tosylester) was transformed to its 11,18-γ-lactone and finally to its 3-dinitrophenylhydrazone. Purification was achieved by 1 paper chromatography and 4 thin-layer chromatographies. The overall-recovery was 10 ± 2.7 (sd)%, n = 134. The non-specific blank was 0.053 ± 0.044 (sd), when determined on water samples, and 0.068 ± 0.034 (sd) ng/5 ml, when determined on adrenalectomised human plasmas (non-specific water blank of the same series: 0.064±0.037 (sd) ng). The addition of a known amount of aldosterone to a plasma resulted in a linear relationship over the range examined: y = (0.947 ± 0.013) × + 0.696, P = 0.000, and aldosterone from 1.0 to 5.0 ng was measured with an accuracy of 95%. Replicate measurements of different volumes of the same plasma from 1.0 to 7.5 ml showed a calculated regression line of y = (0.148 ± 0.005) × −0.01, P = 0.002. Replicate measurements of the same plasma (n = 8) gave a mean value of 0.14±0.01 (sd) ng, a range between 0.13 and 0.15 ng and a coefficient of variation of 7%. Thus, it was possible to determine a peripheral plasma level of 7 ng/100 ml in 2 ml plasma and a level of 3.5 ng/100 ml in 4 ml plasma.