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| Names | |
|---|---|
| IUPAC name 5β-Pregnane-3,20-dione | |
| Systematic IUPAC name (1S,3aS,3bR,5aR,9aS,9bS,11aS)-1-Acetyl-9a,11a-dimethylhexadecahydro-7H-cyclopenta[a]phenanthren-7-one | |
| Other names Pregnanedione | |
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3D model (JSmol) | |
| ChEBI | |
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| Properties | |
| C21H32O2 | |
| Molar mass | 316.485 g·mol−1 |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
5β-Dihydroprogesterone (5β-DHP,pregnanedione, or5β-pregnane-3,20-dione) is anendogenousneurosteroid and anintermediate in thebiosynthesis ofpregnanolone andepipregnanolone fromprogesterone.[1][2][3] It is synthesized from progesterone by theenzyme5β-reductase.[1][4]
5β-DHP has been found to act as apositive allosteric modulator of theGABAA receptor (albeit with anaffinity for thisreceptor regarded as relatively low in comparison to 3α-hydroxylated progesteronemetabolites such as pregnanolone andallopregnanolone)[5] and also as anegative allosteric modulator of theGABAA-rho receptor.[6] In accordance with the former action, it has been found to possessanesthetic,anxiolytic, andantinociceptive effects.[7][5][8][9] 5β-DHP has been found to act as anagonist of thepregnane X receptor (PXR) as well (albeit weakly (EC50 >10,000 μM)),[10] and has been found to regulateuterine contractility through activation of this receptor.[11][12] Unlike5α-dihydroprogesterone, 5β-DHP possesses only very weak affinity for theprogesterone receptor (1.2% of that of progesterone inrhesus monkeyuterus), and in relation to this, is not a notableprogestogen.[13][14]
A study found that 5β-DHP, but not progesterone, directly bound to andantagonized theoxytocin receptor atnanomolarconcentrations, and it was suggested that this may be one of themechanisms by which progesterone maintainspregnancy.[15][16][17] However, a subsequent study was unable to replicate this finding, and there has been no further investigation since.[16] In any case, 5β-DHP has nonetheless been shown to possesstocolytic effects in animals, and this may alternatively be mediated by activation of the PXR.[12]
