Production of C21 steroids in rat fetal ovaries

Female gonads of fetal and neonatal rats were cultured for 24 h in medium 199 supplemented with dibutyryl cyclic AMP (dcAMP), cycloheximide, spironolactone (an inhibitor of 17 alpha-hydroxylase) or hydroxylated cholesterol derivatives. Radioimmunoassays of pregnenolone (P5) and progesterone (P4) were performed in the media. In control medium, progesterone production developed during the second week of life whereas ovaries treated with dcAMP (1 mM) produced progesterone as early as day 14.5 of gestation. The effect of the nucleotide was reversible and the lag period of responsiveness was 12 h. Cycloheximide (1 microgram/ml) added with dcAMP completely inhibited the production of progesterone. Addition of spironolactone to the basal medium was without effect but significantly increased P5 and P4 productions in the presence of dcAMP. The inhibitory effects of spironolactone and trilostane on steroidogenesis were tested in fetal testis. Lastly, the dcAMP effect could not be mimicked with hydroxylated cholesterol derivatives (20 microM). However, an additive effect of 22-hydroxycholesterol was observed in the presence of the nucleotide. These results indicate that the in vitro production of P5 and P4 by fetal ovaries in the presence of dcAMP suggests that dcAMP induces enzymes involved in C21 steroid synthesis. Levels of action of the nucleotide are discussed.