Ultrastructural localization of transferrin synthesis in rat hepatocytes during prenatal and postnatal development

The synthesis of transferrin has been investigated in rat hepatocytes during pre- and postnatal development of the liver by ultrastructural immunoperoxidase cytochemistry. Transferrin was detected in fetal and postnatal hepatocytes on the rough endoplasmic reticulum and in the Golgi apparatus, but the amount and distribution of the protein varied according to the stage of the hepatocyte maturation. Between days 13 and 19 of gestation, nearly all hepatocytes exhibited transferrin. After day 20 of pregnancy more and more unstained hepatocytes were detected. Two periods (19th day of gestation and one day after birth) were characterized by an intense labeling of the Golgi apparatus; in contrast, only a small amount of transferrin was located in this organelle at other stages of the rat liver development. The accumulation of transferrin in the Golgi apparatus is interpreted as a transitory storage of the protein. Transferrin could be produced by immature as well as mature hepatocytes.