A specific antiserum suitable for radioimmunoassay (RIA) of 4-hydroxy-4-androstene-3,17 dione (4-OHA) has been developed. Sheep antiserum was raised by injecting two different conjugates prepared by coupling 4-OHA to ovalbumin. Antisera obtained from a sheep immunised with 4-hydroxy-testosterone-17-hemisuccinate ovalbumin conjugate were of higher titre and more specific than antisera obtained from sheep immunised with 4-hydroxyandrostenedione-7 alpha-carboxyethylthioether. The antiserum bound 50% of 20 picograms of [6,7-3H]-4-OHA at an initial dilution of 1:270. The most relevant steroids, androstenedione (AD) and testosterone (T) were tested and showed cross reactivity of 2.7% and 5.1% respectively. The lower limit of detection was 4.5 pg/tube. Antisera from this animal will prove useful as the basis of a sensitive and specific RIA for clinical pharmacokinetic studies of 4-OHA.
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