Increase in immunoreactivity for endothelin-1 in blood vessels of rat liver metastases: Experimental sarcoma and carcinoma

Using electron immunocytochemistry, blood vessels in the normal rat liver and in 2 different animal models of liver metastases: (1) Hooded Lister rat with MC28 tumour, a sarcoma, and (2) nude rat with HT29 tumour, a carcinoma? were investigated for the presence of endothelin-l. In the normal livers, small subpopulations of vascular endothelial cells displayed discrete immunoreactivity for endothelin-l. In the livers with malignant tumours, there was a substantial increase in endothelin-l-immunoreactive endothelial cells in vessels located at the tumour periphery. In the controls, antibody to endothelin-l also labelled sporadically some fibroblast/fibroblast-like cells associated with the blood vessels. In contrast, intense immunoreactivity for endothelin-l was frequently associated with the tumour cells and/or fibroblast cells in both types of tumour examined.