Maturation and differentiation of cultured fetal stomach. Effects of corticosteroids, pentagastrin, and cytochalasin B.

Gastric mucosa of fetal rats undergoes striking developmental changes during the last few days of gestation in utero. To investigate some aspects of this process, gastric explants from 18-day fetuses (4 days before birth) were maintained in organ culture for 3 days, then assessed by light and electron microscopy. The epithelia from base line uncultured stomachs were stratified and morphologically undifferentiated. During culture in basic medium (Leibovitz L 15), modest maturation of antral and fundic architecture occurred, characterized by epithelial invagination to produce small pit-glands. Secretory granules appeared in occasional epithelial cells, and cytochemistry indicated that most were mucous granules. Addition of pentagastrin (10(-9) to 2 X 10(-7) M) did not induce further morphological maturation in this system. However, addition of cortisol (10(-6) to 10(-5) M) resulted in a marked, dose-related increase of pit-gland formation and of cytological differentiation (appearance of secretory granules). This cortisol-induced architectural maturation was completely inhibited by the mold metabolite cytochalasin B (10(-5) M). The results indicate that fetal gastric maturation can be partially reproduced by culture in chemically defined media, and also suggest that corticosteroids may plan an important role in gastric organogenesis.