Ontogenic appearance of three fatty acid binding proteins in the rat stomach

With the use of specific antibodies against three structurally different fatty acid binding proteins (FABPs), viz, liver FABP (L-FABP), heart FABP (H-FABP), and intestinal FABP (I-FABP), the localization and relative amount of the immunoreactive proteins were determined by immunoblotting and immuno-cytochemistry in the gastric epithelium of rats during prenatal and postnatal development. H-FABP immunoreactivity was first detected at embryonic day 20 (E20), with predominant localization in the parietal cells, whereas I-FABP immunoreactivity was detected at the day of birth in the surface mucous cells. Both immunoreactivities were continuously localized in the same cell types with increasing intensity into adulthood. In contrast, the immunoreactivity for L-FABP showed remarkable changes in intensity and localization during development of the rat stomach. It was first detected in the surface mucous cells of E19. In the first 2 weeks of postnatal life, i.e., the suckling period, L-FABP immunoreactivity reached a peak in intensity and was localized not only in the surface mucous cells, but also in some of the parietal cells, brush cells, and endocrine D cells. In the following few weeks of weaning, the reactivity of surface mucous cells and parietal cells disappeared, leaving only a small amount of total L-FABP immunoreactivity in the adult stomach, which was localized exclusively in the brush cells and D cells. These results revealed that the appearance of the three types of FABPs in the rat stomach is specific to cell types and developmental stages.