DIFFERENTIATION OF OXYNTIC CELLS DURING EARLY ONTOGENY IN THE BOVINE

The origin and the differentiation of oxyntic cells in fetal bovine ab omasum were investigated using transmission electron and light microsc opic methods. In the oxyntic gland region oxyntic cell precursors and immature oxyntic cells appear as early as at the end of the first trim ester of gestation - much earlier than described in any other mammalia n animal species. Immature oxyntic cells are characterized by long api cal microvilli, by their triangular-shaped light cytoplasm rich in lar ge and numerous mitochondria, by the existence of vesicular profiles a nd by the incipient invagination of the apical plasma membrane forming a primitive intracellular canaliculus expanding into central areas of the cell. The oxyntic cell represents the first exocrine cell type de veloping from secretory granule-containing cells in the base of the pr imitive gastric glands.