Localization of transforming growth factor-beta receptor types I, II, and III in the postnatal rat small intestine

Transforming growth factor-beta 2 (TGF-beta 2) levels in rat milk are high in early lactation, whereas endogenous TGF-beta 1 expression in the neonata l gut increases toward midweaning. Three types of transmembrane TGF-beta re ceptors have been identified in mammals. The receptor III (or betaglycan) b inds and presents TGF-beta 1 or beta 2 to receptor II. Receptor I then inte racts with receptor II, forming a signaling receptor complex, and propagate s the signal. To determine whether TGF-beta receptor expression in the gut is also developmentally regulated, the present study assessed ontogeny of T GF-beta receptor expression in the postnatal rat small intestine. Jejunum a nd ileum tissues from rat pups at d 3, 10, 14, 21, and 28 of age were colle cted. Cryostat sections were stained with antibodies against TGF-beta recep tors I, LI, and III, and various cell markers by immunofluorescence. In bot h regions, receptor I staining was seen on apical and basolateral membranes of the villus and crypt epithelium at all ages, and staining on the apical membrane increased with age; receptor II was predominantly expressed in th e crypt, and staining on the villi appeared after d 10; receptor III was di stributed throughout the mucosa at early ages but diminished from the epith elium postweaning by d 28. T cells, B cells, and dendritic cells in the lam ina propria expressed TGF-beta receptor III but lacked expression of recept or I and II. The pattern of TGF-beta receptor expression changes with age i n a manner that may reflect the change in ligand from TGF-beta 2 (milk-deri ved) to TGF-beta 1 (endogenously produced).