N-cadherin is known to be expressed in neuroectodermal tissue such as central nervous system and various mesodermal origin tissues such as kidney and heart. We investigated N-cadherin expression in the endocardial cushion in developing rat heart by immunohistochemical method.

Fetal rat hearts at the 11th, 13th, 15th, 17th, and 19th day of gestation and the 1st day neonatal rat heart were used. Hematoxylin and eosin stain was performed for normal cardiogenesis, and immunohistochemistry was performed for the expression of N-cadherin in interventricular septum(IVS) during cardiogenesis in rat.

Ventricular wall and membranous part of the IVS showed positive reaction with anti-N-cadherin at the 11th day of gestation. Membranous part of IVS was begun to show tracely positive reaction at the 15th day of gestation, and thereafter the immunoreactivity was increased with maturation. At the 17th day of gestation mesenchymal cells in membranous muscular part of the IVS showed positive reaction. The similar immunoreactivity of membranous and muscular parts of IVS were shown at the 19th day of gestation.

As the immunoreaction of mesenchymal cells in the membraneous part of IVS to anti-N-cadherin was increased with time, it is suggested that mesenchymal cells in membranous part of IVS were differentiated into the cardiomyocytes.