Abstract
The localization of nitric oxide synthase (NOS) in rabbit aorta was investigated by electron-immunocytochemistry. Using the pre-embedding peroxidase-antiperoxidase technique, a neuronal isoform (type I) of NOS was localized in a small subpopulation of endothelial cells (approximately 5–6% of all observed cell profiles). This finding indicates that the endothelium of rabbit aorta is heterogeneous. Together with the post-embedding immuno-gold technique the results showed that the immunolabelling was predominantly in the cytoplasm of endothelial cells. In particular, a relation of gold particles with ribosomes was evident but no labelling in cytoplasmic vesicles was observed. Immunoreactivity for NOS was also localized extracellularly between the endothelial cells and the inner muscle layers.