Decrease in the expression of the 3beta-hydroxysteroid dehydrogenase gene in human adrenal tissue during prepuberty and early puberty: implications for the mechanism of adrenarche

Adrenarche is the increase of adrenal androgen secretion, mainly dehydroepiandrosterone and dehydroepiandrosterone sulfate, that occurs during prepuberty in higher primates. This event takes place at about 6-8 y of age in humans. It had been postulated that adrenarche might reflect an increase in the 17,20 lyase:17OH-ase activity ratio of microsomal cytochrome P450c17. However, studies to demonstrate this mechanism have been unsuccessful. Because it has been described that virilizing adrenocortical carcinomas have high dehydroepiandrosterone sulfate secretion and low 3beta-hydroxysteroid dehydrogenase (3betaHSD) activity, in this study we evaluated the possible existence of maturative changes of the level of 3betaHSD type II mRNA in 11 normal prepubertal and early pubertal human adrenals. Adrenal glands from subjects aged 0.1 to 13 y were obtained from organ donors, patients undergoing resection of the kidney for renal neoplasms or necropsies with less than 6 h of postmortem time. The expression of 3betaHSD type II gene was studied by dot blot in all samples and by relative reverse transcriptase (RT)-PCR in nine samples. The size of the transcripts was evaluated by Northern blot. Hybridization was performed using labeled human 3betaHSD cDNA probes. The uniformity of loading was tested using labeled human beta actine cDNA. The relative intensities of hybridization signals were quantified by scanning densitometry. The expected bands after relative RT-PCR were eluted, and radioactivity was measured in a scintillation counter. For the analysis of the results, subjects were divided into two groups as a function of age: group 1, less than 8 y (n = 6; range 0.1-2.48 y) and group 2, equal or older than 8 y (n = 5; range 8-13 y). 3BetaHSD type II mRNA expression, analyzed by dot blot and relative RT-PCR, was significantly higher (p < 0.05) in group 1 (median and range 4.99, 0.50-8.00 and 16.3, 13.5-40.0 arbitrary units, respectively) than in group 2 (0.15, 0.12-0.75 and 5.66, 3.18-13.0, respectively). In conclusion, we have shown a decrease of the expression 3betaHSD type II gene as a function of age in prepubertal and early pubertal normal human adrenal tissue. This maturative change might be involved in the mechanism of human adrenarche.