Laminin 2 (merosin), but not laminin 1 (EHS-laminin), may be a major laminin isoform present in normal and fibrotic rat liver

Recently several laminin isoforms were newly identified and found to distri bute in a tissue and cell type-specific manner. We have studied the express ion of several laminin isoforms, including alpha 1(A), alpha 2(M), beta 1(B 1), beta 2(S), and gamma 1(B2) subunits, in normal and CCl4-induced fibroti c rat liver by RT-PCR and performed immunohistochemical study with newly de veloped monoclonal antibody to merosin (laminin-2). RT-PCR study for lamini n subunits revealed that alpha 2(M) subunit mRNA transcript was dominant ch ain present in normal rat liver tissue, but alpha 1(A) subunit mRNA was not . Laminin beta 1(B1) and gamma 1(B2) subunit mRNA were detected strongly an d beta 2(S) subunit mRNA was detected weakly. During the CCl4-induced rat h epatic fibrosis, alpha 2, beta 1, beta 2, and gamma 1 subunit mRNA showed i ncreased expression, but alpha 1 transcript could not be detected during fi brotic process even in the condition where alpha 1 subunit mRNA was detecta ble in rat placental tissue. Immunohistochemical studies with a novel monoc lonal antibody to merosin also revealed that deposition of merosin increase d during CCl4-induced rat fibrotic liver. These data strongly suggest that laminin isoform containing alpha 2 subunit (merosin) may be a major laminin present in normal and fibrotic rat liver. (C) 1999 Elsevier Science Irelan d Ltd. All rights reserved.