Autoradiographic localization of 125I-big endothelin-1 in rat tissues.

Endothelin-1 (ET-1), a potent vasoconstrictor with a characteristically long-acting activity in vitro and in vivo, is thought to be generated in endothelial cells from a less active intermediate, big endothelin-1 (big ET-1). In addition to ET-1, big ET-1 is also present in the circulation. The autoradiographic localization of 125I-big ET-1 has been studied after intravenous administration in rat tissues. Highest enrichment of radioactivity was found in the kidney cortex. Compared to blood levels, enrichment of radioactivity is also detected, especially in the vascular wall of the aorta. Comparing the radioactivity pattern of ET-1 and big ET-1, a nearly identical tissue distribution is observed, with the exception of the relative enrichment in the lung, the endocardium and the zona glomerulosa.