title: Origin of the apical transcytic membrane system in jejunal absorptive cells of neonates.
abstract: We investigated the origin of the apical transcytic membrane system in jejunal absorptive cells of neonatal rats using light, electron, and immunofluorescence microscopy. In rats just after birth, intraluminally injected horseradish peroxidase (HRP), used as a macromolecular tracer, was observed only in the apical endocytic membrane system including the lysosomes, of jejunal absorptive cells in vivo. No tracer, however, was found in the intercellular space between the jejunal absorptive cells and the submucosa. Immunoreactive neonatal Fc receptor (FcRn) was localized in the perinuclear region of these absorptive cells whereas immunoglobulin G (IgG) was not found in these absorptive cells. In contrast, in rats 2 h after breast-feeding, intraluminally injected HRP was observed in the apical endocytic membrane system and in the apical transcytic membrane system of the absorptive cells. Moreover, HRP was found in the intercellular space between the jejunal absorptive cells and the submucosa. Furthermore, FcRn and IgG were widely distributed throughout the absorptive cells, and IgG was detected in both the intercellular space and the submucosa. These data suggest that initiation of breast-feeding induces the transportation of membrane-incorporated FcRn from its perinuclear localization to the apical plasma membrane domain. This transportation is achieved through the membrane system, which mediates apical receptor-mediated transcytosis via the trans-Golgi network. Subsequently, the apical plasma membrane containing the FcRn binds to maternal IgG, is endocytosed into the absorptive cells, and is transported to the basolateral membrane domain.
authors: Graduate School of Health and Nutrition Sciences, Nakamura Gakuen University, 5-7-1 Befu, Jyonan-ku, Fukuoka, 814-0198, Japan.
authors: Nana
authors: N
authors: Kumagai
authors: Ryoko
authors: R
authors: Baba
authors: Yoshiko
authors: Y
authors: Sakuma
authors: Kumi
authors: K
authors: Arita
authors: Miki
authors: M
authors: Shinohara
authors: Megumi
authors: M
authors: Kourogi
authors: Sunao
authors: S
authors: Fujimoto
authors: Mamoru
authors: M
authors: Fujita
mesh_terms: D000042:Absorption; D000818:Animals; D000831:Animals, Newborn; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000378:metabolism / Q000648:ultrastructure; D006735:Horseradish Peroxidase; D007074:Immunoglobulin G / Q000378:metabolism / Q000648:ultrastructure; D007583:Jejunum / Q000378:metabolism / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D009928:Organ Specificity; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D011961:Receptors, Fc / Q000378:metabolism / Q000648:ultrastructure; D057900:Transcytosis / Q000502:physiology*; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D015395:Histocompatibility Antigens Class I; D007074:Immunoglobulin G; D011961:Receptors, Fc; D006735:Horseradish Peroxidase; C100688:Fc receptor, neonatal