Endothelin Expression During Rat Heart Development: An Immunohistochemical and in Situ Hybridization Study

To investigate the mitogenetic role of endothelins (ETs) in the heart, an ontogenetic analysis using immunohistochemistry and in siru hybridization was made in the Wistar rat embryonic heart from early embryonic day (E) 9 to E20.Mature ET peptides were detected by immunohistochemistry from E10 to E18 in almost all the atrial and ventricular cardiac myocytes and disappeared after E19.ET-1 mRNA was detected in atrial and ventricular cardiac myocytes by in sizfu hybridization from E12 to E18 and disappeared after E19.ET-3 mRNA was detected in atrial and ventricular cardiac myocytes by in siru hybridization from E10 to E18 and disappeared after E19.In situ hybridization and immunohistochemistry allowed visualization of ET-1 and ET-3 synthesis and secretion, respectively: ET-3 was first synthesized and secreted at E10, followed after 2 days by ET-1 expression.Both ET-1 and ET-3 were present throughout the period of heart development and the relation between the ET