Localisation of nitric oxide synthase and its colocalisation with vasoactive peptides in coronary and femoral arteries. An electron microscope study

The localisation and colocalisation of neuronal isoform (type I) nitric oxide synthase, endothelin-1, arginine-vasopressin and substance P in endothelial cells of rat coronary and femoral arteries was investigated by pre-embedding and postembedding immunocytochemistry. Nitric oxide synthase appeared in a high proportion of endothelial cells of both arteries (about 89 % in the femoral artery, examined with the pre-embedding avidin-biotin-peroxidase method, and in almost all cells of the coronary artery, examined with the postembedding immunogold technique). Double immunogold labelling in single cells demonstrated the colocalisation of nitric oxide synthase with endothelin-1, arginine-vasopressin and substance P. The immunolabelling was mostly confined to the cytoplasmic matrix. It is suggested that nitric oxide synthase/nitric oxide and the peptides examined may be involved in local control of blood flow in coronary and femoral arteries.