Corticosteroids in Human Blood: I. Determination of Free and Conjugated 17-Hydroxycorticosteroids in Plasma

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Abstract
A simple yet sensitive and reproducible method has been developed for the estimation of free and conjugated 17-hydroxycorticosteroids (17-OHCS) in plasma. A new extraction procedure for the conjugates yielded extracts which, after evaporation to dryness, produced 5–10 times less intense “background” color with the sulfuric acid of the Porter-Silber (P-S) reagent than any other method tested. A simultaneous determination of free and conjugated 17-OHCS in 12 plasma specimens, using this method, can be completed easily by one technician within 2 working days. Furthermore, a technique has been developed which permits a separate estimation of the glucuronide and the solvolyzable (presumably sulfate) fractions of the conjugated 17-OHCS. Using this technique, it was possible to demonstrate the consistent presence of solvolyzable P-S chromogens in all the plasma samples examined. The steroidal nature of the material measured has been proved by the classic method for the isolation and identification of steroidal compounds.