Endothelin. Immunohistologic localization in aorta and biosynthesis by cultured human aortic endothelial cells

Endothelin-1 (ET-1) has been shown to exist in many organs and to have various biologic functions including vasoconstriction. However, an exact location of ET gene expression of the tissues is not fully investigated. Human aortic tissue was examined to elucidate the exact location of ET gene expression.

Human aortas were obtained at autopsy and fixed in either conventional 10% formalin or 3% paraformaldehyde. The aortic thin sections were subjected to examinations of an immunohistochemistry and in situ hybridization of ET-1. Human aortic endothelial cells were cultured by a previously reported method. ET-1 released in the supernatant from the cultured endothelial cells was radioimmunoassayed.

Immunohistologic study of ET-1 revealed a linear staining of the endothelial monolayer and diffuse staining in the intimal and medial smooth muscle cells on human aorta except for fetal aorta. In situ hybridization signals were intense in the endothelial cells from the elderly as well as younger subjects as examined with 35S-labeled anti-sense probe RNA. Fetal aortic endothelial cells revealed the least signals that meant developing but still immature gene translation. Smooth muscle cells showed positive but weak in situ hybridization signals. Control immunohistologic and hybridization studies were negative. ET-1 biosynthesis by cultured human aortic endothelial cells was invariably low in the subjects under the age of 50, ranging from 0.23 to 0.40 pmol/1 x 10(5) cells for 3 days. On the other hand, endothelial cells from the elderly subjects generally synthesized a greater amount of endothelin in vitro.

These findings indicate that ET-1 is most highly expressed in endothelial cells, although not as highly but certainly, expressed in intimal and medial smooth muscle cells. This fact gives a new insight into the biophysiologic and pathologic roles of ET. In addition, these methods are applicable to investigate the gene expression of ET-1 in all organs and tissues.