Laminin Isoforms and Laminin-Producing Cells in Rat Anterior Pituitary

Laminin is a key component of the basement membrane and is involved in the structural scaffold and in cell proliferation and differentiation. Research has identified 19 laminin isoforms, which are assemblies of alpha, beta, and gamma chains (eg, the alpha 1, beta 1, and gamma 1 chains form the laminin 111 isoform). Although laminin is known to be present in the anterior pituitary, the specific laminin isoforms have not been identified. This study used molecular biological and histochemical techniques-namely, RT-PCR, immunohistochemistry, and in situ hybridization-to identify the laminin isoforms and laminin-producing cells in rat anterior pituitary. RT-PCR showed that laminin alpha 1, alpha 3, and alpha 4 genes were expressed in anterior pituitary. Immunohistochemistry revealed laminin alpha 1 in gonadotrophs and laminin alpha 4 in almost all vascular endothelial cells. Laminin alpha 3 was seen in a subset of vascular endothelial cells. We then performed in situ hybridization to localize beta and gamma chains in these cells and found that laminin beta 1, beta 2, and gamma 1 were expressed in gonadotrophs and that laminin beta 1 and gamma 1 were expressed in endothelial cells. In conclusion, we identified gonadotroph-type (laminin 111 and 121) and vascular-type (laminin 411 and 311) laminin isoforms in rat anterior pituitary.