A combined radioimmunoassay for the measurement of unconjugated and sulfoconjugated pregnenolone, 17 hydroxypregnenolone, dehydroepiandrosterone, and estrone applied to fetal and maternal ovine plasma
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Abstract
This report describes a radioimmunoassay (RIA) method for the combined measurement
of four steroid sulfoconjugates and their four unconjugated counterparts in maternal
and fetal ovine plasma: pregnenolone (delta 5P), 17-hydroxypregnenolone (17 delta
5P), dehydroepiandrosterone (DHEA), and estrone (E1). In the procedure a preliminary
ether extraction is utilized to isolate the unconjugated steroids followed by salting
out, ethyl acetate extraction, and mineral acid solvolysis of the remaining sulfated
steroids. The hydrolyzed sulfoconjugates are then separated chromatographically and
measured in a manner identical to their unconjugated counterparts. The combined measurement
of these eight steroids in single samples of fetal and maternal ovine plasma has not
been reported previously and plasma concentrations of these steroids were heretofore
unknown. Since no previous data was available for comparison, rigorous specificity
evaluation of this RIA system was required prior to its use for physiologic studies
and the reporting of concentrations in this species.