Radioimmunoassay of 5α-Pregnane-3,20-Dione
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A radioimmunoassay (RIA) procedure has been developed for the measurement of 5α-pregnane-3,20-dione (DHP) in human plasma after ether extraction of the plasma-samples, followed by column chromatography. The antiserum was generated in rabbits with 6α-carboxyethylmer-captoprogesterone-BSA conjugate. The high affinity (Ka = 3.72 × 109 1/mol) antiserum binds 40% of 40 picograms of tritiated 5α-pregnane-3,20-dione at working dilutions of 1 : 2800. Negligible cross-reactivity of the antiserum was detected with 5β-pregnane-3,20-dione (1.8%). Other hydroxylated preg-nanes showed minor cross-reactivity (5–40%). The cross-reacting steroids were all separated from pregnanedione by one chromatographic step. The plasma levels of 5α-pregnane-3,20-dione were measured from 22nd to 42nd week of normal pregnancy and compared to published data.
Key wordsPregnancy 5α-Pregnane-3,20-dione Radioimmunoassay
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