Progesterone 20 alpha-dihydroprogesterone and 20 beta-dihydroprogesterone levels in different compartments from the human foeto-placental unit.

The endogenous levels of progesterone, 20 alpha-dihydroprogesterone and 20 beta-dihydroprogesterone in different foetal tissues, in placental tissue and in foetal blood during pregnancy (week 9-25) were determined by gas-liquid chromatography or by radioimmunoassay. The identification of these steroids in foetal tissues was based on the behaviour in paper and thin-layer chromatography, the formation of different derivatives, and the retention times in gas-liquid chromatography. For additional identification of progesterone and 20 alpha-dihydroprogesterone a mass spectrum was obtained. The average concentrations of progesterone (P), 20 alpha-dihydroprogesterone (20 alpha-DHP) and 20 beta-dihydroprogesterone (20 beta-DHP) in foetal tissues were as follows (ng/g wet weight tissue): brain, P 119.0 +/- 45.5, 20 alpha-DHP 86.9 +/- 44.7 and 20 beta-DHP 9.7; lungs, P 257.7 +/- 195.7, 20 alpha-DHP 60.3 +/- 26.4 and 20 beta-DHP 7.8; liver, P 103.7 +/- 84.6, 20 alpha-DHP 95.2 +/- 89.8 and 20 beta-DHP 17.8; adrenals, P 295.7 +/- 90.0 20 alpha-DHP 254.5 +/- 194.6; kidneys, P 214.2 +/- 155.3 and 20 alpha-DHP 76.6 +/- 43.0; intestine, P 273.2 +/- 166.7, 20 alpha-DHP 77.9 +/- 51.2 and 20 beta-DHP 8.7; residual tissues, P 246.3 +/- 178.3 and 20 alpha-DHP 54.8 +/- 44.5. The average concentrations in placental tissue and in foetal plasma (week 12-18) were as follows (ng/g wet weight tissue or ng/ml plasma): placenta, P 2619. +/- 2153.6 and 20 alpha-DHP 461.0 +/- 155.9; foetal plasma, P 378.7 +/- 231.8 and 20 alpha-DHP 283.0 +/- 108.9. These results indicate that some foetal organs contain a high 20 alpha-reductase activity at least during the first half of pregnancy.