Immunoelectron microscopy pinpoints glutathione-peroxidase (GSH-PO) in neonatal rat adrenal cortical cells

Localization of glutathione-peroxidase (GSH-PO) in adrenal cortical cells of neonatal rats were determined by immunocytochemical analysis. GSH-PO first appeared 14 days after birth. Intracellular localization of GSH-PO was mainly in cytosol (cytosol GSH-PO) but no intramitochondrial localization of GSH-PO was detected. Twenty-one days after birth, intramitochondrial localization of GSH-PO (mitochondrial GSH-PO) was present. Mitochondrial GSH-PO depends on ACTH stimulation; therefore, its presence in the adrenal cortical cells of neonatal rats may be the morphologic expression of the gradual acquisition of adult metabolic features during steroidogenesis. The intracellular GSH-PO staining pattern in adrenal cortical cells therefore should be a useful marker for steroidogenesis.