Determination of endothelin-converting enzyme activity by high-performance liquid chromatography-on-line radioactive flow monitoring.

A rapid method to investigate the metabolism of 125I-labelled or non-labelled human big endothelin to endothelin-1 by reversed-phase high-performance liquid chromatography (HPLC) and on-line radioactive flow monitoring and/or ultraviolet detection was developed. Samples were processed by solid-phase extraction (average recovery 70-80% for non-labelled and 20-25% for 125I-labelled big endothelin and endothelin-1) followed by HPLC analysis (total analysis time 20 min). The method was successfully employed to monitor the conversion of big endothelin to endothelin-1 by various blood-borne cells, such as human polymorphonuclear leukocytes or monocytes/macrophages.