ABSTRACT
The stomach of the rat undergoes extensive changes during the formation and maturation of gastric glands. The presence of transforming growth factor beta (TGFbeta) in rat milk and in the gastrointestinal tract of pups may suggest its role in this process. The current study evaluated the in vivo dynamic expression and distribution of TGFbeta1, beta2, beta3 and their receptors TbetaRI and TbetaRII in the gastric epithelium of 20-day fetal rats and 1-, 14-, 21-, and 30-day-old pups. Immunohistochemistry was used to detect the proteins, and staining was classified according to intensity and cell type. The results showed that the gastric epithelium expresses TGFbeta isoforms and receptors throughout development. We found that immunoreactivity paralleled the appearance of differentiated cells, such that surface mucous cells were the first to be immunostained and chief cells were the last. The intensity of reactions followed this same pattern, showing that the expression of TGFbeta isoforms spread along the gland with growth. Of interest, the highest apparent activity of TGFbeta was observed from 21 days onward, a period that is concomitant with weaning and maturation of most gastric cell types. In addition, surface mucous cells were strongly labeled at the basal cytoplasm at 14 days, suggesting an interaction with the connective tissue. In conclusion, the dynamic expression of TGFbeta1, beta2, beta3, and TbetaRI and TbetaRII through stomach development suggests significant paracrine and autocrine roles for this growth factor. We propose that temporal and spatial differences may be regulated by dietary changes, which in turn control cell proliferation and differentiation in the gastric epithelium.
