ELISA of 6-beta-hydroxycortisol in human urine: diurnal variations and effects of antiepileptic therapy.

An enzyme-linked immunosorbent assay for urinary 6-beta-hydroxycortisol (6-beta-OHF) was developed. A highly specific antiserum against 6-beta-OHF-21-hemisuccinate bovine serum albumin (6-beta-OHF-21-HS-BSA) raised in rabbit was used. The enzyme-labelled hapten was prepared by the mixed anhydride method using horse radish peroxidase (HRP). The limit of detection is very low (10 pg), the intra-assay variation ranges from 5.2-6.6%, the inter-assay variation is 8.2-8.3%. Cross reactivities of various steroids are very low. The diurnal variations in urinary 6-beta-OHF and it's ratio to 17-hydroxycorticosteroids (17-OHCS) were studied in six healthy volunteers. No significant difference was found within the 24 h for the ratio of 6-beta-OHF to 17-OHCS. A large increase of 8-12 h urinary 6-beta-OHF was observed in patients receiving chronic treatment with antiepileptics.