Dichlorodiphenyltrichloroethane (DDT) is the most widespread persistent pollutant with endocrine-disrupting properties. DDT has been shown to disrupt secretory and morphogenetic processes in the adrenal cortex. The present investigation aimed to evaluate transcriptional regulation of postnatal growth of the adrenal medulla and formation of the pools necessary for self-renewal of medullary cells in rats that developed under low-dose exposure to DDT. The study was performed using male Wistar rats exposed to low doses of o,p'-DDT during prenatal and postnatal development. Light microscopy and histomorphometry revealed diminished medulla growth in the DDT-exposed rats. Evaluation of Ki-67 expression in chromaffin cells found later activation of proliferation indicative of retarded growth of the adrenal medulla. All DDT-exposed rats exhibited a gradual decrease in tyrosine hydroxylase production by adrenal chromaffin cells. Immunohistochemical evaluation of nuclear β-catenin, transcription factor Oct4, and ligand of sonic hedgehog revealed increased expression of all factors after termination of growth in the control rats. The DDT-exposed rats demonstrated diminished increases in Oct4 and sonic hedgehog expression and lower levels of canonical Wnt signaling activation. Thus, developmental exposure to the endocrine disruptor o,p'-DDT alters the transcriptional regulation of morphogenetic processes in the adrenal medulla and evokes a slowdown in its growth and in the formation of a reserve pool of cells capable of dedifferentiation and proliferation that maintain cellular homeostasis in adult adrenals.
Keywords: DDT; Oct4; Shh; adrenal medulla; endocrine-disrupting chemicals; growth; self-renewal.