Radioimmunoassay of 3α-hydroxy-5α-pregnan-20-one in rat and human plasma

Robert H. Purdy, Perry H. Moore, P. Narasimha Rao, Nobuyoshi Hagino, Tatsumi Yamaguchi, Peter Schmidt, David R. Rubinow, A. Leslie Morrow, Steven M. Paul

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203 Scopus citations


A radioimmunoassay for measuring 3α-hydroxy-5α-pregnan-20-one in plasma has been developed. Polyclonal antibodies were raised in rabbits against 3α-hydroxy-20-oxo-5α-pregnan-11α-yl carboxymethyl ether coupled to bovine serum albumin. 3α-Hydroxy-5α-pregnan-20-one was purified from ether extracts of plasma by high-performance liquid chromatography. These antibodies were then used for the radioimmunoassay of this centrally active progesterone metabolite in rat and human plasma. 3α-Hydroxy-5α-pregnan-20-one was detected in plasma from female rats on the day ofestrus (2.0 to 9.3 ng/ml) and in the plasma of women during the luteal phase of the menstrual cycle at levels ranging from 0.25 to 2.5 ng/ml. The latter was highly correlated with plasma progesterone levels.

Original languageEnglish
Pages (from-to)290-296
Number of pages7
Issue number7
StatePublished - Jul 1990


  • allopregnanolone
  • plasma RIA
  • progesterone
  • steroids


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