Immunohistochemical Study of the Laminin α5 Chain and Its Specific Receptor, Basal Cell Adhesion Molecule (BCAM), in both Fetal and Adult Rat Pituitary Glands

Laminin, a major basement membrane protein, comprises three subunit chains: alpha, beta, and gamma chains. Among these chains, only the laminin alpha chain is capable of signaling via laminin receptors. Although laminin isoforms containing the alpha 5 chain were reported to be the first laminin produced during rat anterior pituitary gland development, the functions of these isoforms are unknown. We used immunohistochemical techniques to localize the laminin alpha 5 chain and its specific receptor, basal cell adhesion molecule (BCAM), in fetal and adult pituitary gland. Laminin alpha 5 chain immunoreactivity was observed in the basement membrane of the primordial adenohypophysis at embryonic days 12.5 to 19.5. Double immunostaining showed that BCAM was present and co-localized with the laminin alpha 5 chain in the tissue. Quantitative analysis showed that the laminin alpha 5 chain and BCAM were expressed in the anterior pituitary gland during postnatal development and in adulthood (postnatal day 60). In the adult gland, co-localization of the laminin alpha 5 chain and BCAM was observed, and BCAM was detected in both the folliculo-stellate cells and endothelial cells. These results suggest that laminin alpha 5 chain signaling via BCAM occurs in both the fetal adenohypophysis and adult anterior pituitary gland.