DETERMINATION OF DEHYDROEPIANDROSTERONE AND DEHYDRO- EPIANDROSTERONE SULPHATE IN HUMAN PLASMA USING ELECTRON CAPTURE DETECTION OF 4-ANDROSTENE-3,6,17-TRIONE AFTER GAS-LIQUID CHROMATOGRAPHY

A method for the measurement of dehydroepiandrosterone (DHA) and of its sulphate (DHAS) in human peripheral plasma is described and evaluated. After isolation of DHA from the sample the steroid is oxidized to 4\x=req-\ androstene-3,6,17-trione, which is measured with an electron capture detector after gas\p=m-\liquidchromatography. It is possible to detect 100 pg 4-androstene-3,6,17-trione. The smallest amount of DHA per sample that can be distinguished from zero is approximately 4 ng, when recovery (27\m=.\9 \m=+-\ 8\m=.\8%) and method blank (0\m=.\23\m=+-\0\m=.\38ng) are taken into account. The oxida-tion to 4-ene-3,6-diones is specific for steroidal 5-en-3-ols. Specificity for DHA is ensured by several chromatographic steps. Repeated estimation of 10 ng DHA gave a mean value of 9\m=.\6\m=+-\1\m=.\45(s.d.) ng (n = 35). Mean concen-trations and their standard deviations for DHA and DHAS in peripheral plasma from 18 individuals were 0\m=.\50\m=+-\0\m=.\25and 78 \m=+-\40 \g=m\g/100ml, respec-tively, at 08.30 h and 0\m=.\32\m=+-\0\m=.\17and 84 \m=+-\34 \g=m\g/100ml, respectively, at 17.00 h of the same day. Levels ofplasma cortisol in the same plasma samples estimated with a competitive protein-binding method were 16\m=.\71\m=.\8and 11\m=.\9\m=+-\3\m=.\8\g=m\g/100ml, respectively. No significant differences between the sexes were observed by any of the three assays. The mean values of the plasma concentrations of cortisol and DHA in the morning were significantly higher than those in the evening (P < 0\m=.\001and P < 0\m=.\005,respectively). In contrast, the mean value of the plasma levels of DHAS in the morning was significantly lower than that in the evening (P < 0\m=.\025)