CONVERSION OF BIG ENDOTHELIN-1 TO ENDOTHELIN-1 BY 2 TYPES OF METALLOPROTEINASES DERIVED FROM PORCINE AORTIC ENDOTHELIAL-CELLS

Incubation of big endothelin-1 (big ET-11-39) with either the cytosolic or membrane fraction obtained from cultured endothelial cells, resulted in an increase in immunoreactive-endothelin (IR-ET), which was markedly inhibited by metal chelators. Phosphoramidon, a metalloproteinase inhibitor, specifically suppressed the membrane fraction-induced increase in IR-ET, whereas the increase in IR-ET observed with the cytosolic fraction was not influenced by phosphoramidon. Reverse-phase (RP)-HPLC of the incubation mixture of big ET-1 with the cytosolic or membrane fraction revealed one major IR-ET component corresponding to the elution position of synthetic ET-11-21. Simultaneously, immunoreactivities like the C-terminal fragment (CTF22-39) of big ET-1 were present, as deduced from the RP-HPLC coupled with the radioimmunoassay for CTF. Our results indicate the presence of two types of metalloproteinases, which convert big ET-1 to ET-1 via a single cleavage between Trp21 and Val22, in vascular endothelial cells. © 1990.