RESUMEN
The relation between the expression of the oxyntic cell phenotype and the modifications of the extracellular matrix during development of the gastric glands, was studied in 10 to 21 day-old chick embryos. Cytodifferentiation of the oxyntic cells was established by ultrastructural methods, while the expression of pepsinogen, mitochondrial enzyme markers and apical secretory membranes was determined by histochemical and biochemical procedures. Results show that the morphogenesis of the glandular lobules occurs between days 8 and 15 of gestation. Later on, the lobules enlarge but maintain their basic morphology. Until day 13, the developing glands consist of primary tubes lined by a stratified columnar epithelium. The apical poles of the cells that contact the lumen show cytoplasmic processes, and Mg-ATPase activity and F-actin are concentrated at the apical cell borders. From day 13 on, the cells of the simple epithelium that lines secondary tubules budding from the primary tube, show all the features that define differentiated oxyntic cells. The synthesis of glycosaminoglycans during glandular morphogenesis was studied measuring the incorporation of radioactive sulfate into developing chick embryo proventriculi. An important increase in isotope incorporation was found between days 13 and 18 of development. Histochemical localization of these macromolecules shows that glycosaminoglycans are closely associated with the developing glandular lobules. Variations in the structure of epithelial cells undergoing morphogenesis and in the composition of the extracellular matrix are synchronous, suggesting that interactions between them may be significant in terms of the establishment and maintenance of the adult gastric gland phenotype