MORPHOLOGICAL STUDY ON THE PRODUCTION AND SECRETION MECHANISM OF HUMAN CHORIONIC GONADOTROPIN (hCG)

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The present paper describes the production and secretion mechanisms of human chorionic gonadotropin (hCG). In order to determine more detailed mechanisms of production and secretion of hCG, a morphological study was done by ultrastructural, histochemical and immunohistological examinations using β-subunit of hCG (β-hCG), which is the determinant of both the biological and immunological activity of hCG.
Small pieces of human chorionic tissue were collected from pregnant women in an early stage of gestation (mainly in the seventh and eighth week) by curette or at hysterectomy. Human chorionic gonadotropin and its subunits are a kind of glycoprotein, which is represented by a saliva-insoluble PAS positive substance in syncytial trophoblast. The substance appears as secretion granules in electron microscopic study. Fine granules appear first in the perinuclear Golgi zone with a surrounding smooth dense membrane, and gradually increase in size toward the cell surface where liquefaction and liberation into the maternal blood occur.
Immunohistology reveals mostly the same process of production and secretion of granular β-hCG only in syncytial trophoblast.
Comparative morphology among electron microscopy, histochemical and immunohistological examinations lead us to the conclusion that hCG, which is produced only in the syncytial trophoblast, appears as granules in intra-cytoplasmic distribution as well as mechanisms of production and secretion.