Differential proteomic analysis of adrenal gland during postnatal development

The adrenal glands (AGs) are endocrine organs essential for life. They undergo a fetal to adult developmental maturation process, occurring in rats during the first postnatal month. The molecular modifications underlying these ontogenic changes are essentially unknown. Here we report the results of a comparative proteomic analysis performed on neonatal (Postnatal day 3) versus adult (Postnatal day 30) AGs, searching for proteins with a relative higher abundance at each age. We have identified a subset of proteins with relevant expression in each developmental period using 2-DE and DIGE analysis. The identified proteins belong to several functional categories, including proliferation/differentiation, cell metabolism, and steroid biosynthesis. To study if the changes in the proteome are correlated with changes at the mRNA level, we have randomly selected several proteins with differential expression and measured their relative mRNA levels using quantitative RT-PCR. Cell-cycle regulating proteins (retinoblastoma binding protein 9 and prohibitin) with contrasting effects on proliferation are expressed differentially in neonatal and adult AG. Progesterone metabolizing enzymes, up-regulated in the neonatal gland, might contribute to the hyporesponsiveness of the adrenal cortex characteristic of this developmental period. We have also observed in the adult gland a marked up-regulation of enzymes involved in NAD(P)H production, thus providing the reducing power necessary for steroid hormone biosynthesis.