Release of immunoreactive endothelin from porcine aortic strips.

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Abstract
The present study was designed to determine whether endothelin and "big endothelin" are released from aortic strips with endothelium and to examine the effect of thrombin by using a specific radioimmunoassay. Porcine aortic strips with endothelium released immunoreactive endothelin (ir-endothelin) and immunoreactive big endothelin (ir-big endothelin) into the medium in a time-dependent manner. These releases were markedly inhibited by 10 micrograms/ml cycloheximide. Expectedly, after removal of endothelium, aortic strips did not release a detectable amount of ir-endothelin and ir-big endothelin. In contrast, thrombin (10 units/ml) significantly stimulated the release of ir-endothelin and ir-big endothelin. Reverse-phase high-performance liquid chromatography coupled with radioimmunoassay revealed that the major component of ir-endothelin corresponds to standard endothelin-1 (1-21) and the major component of ir-big endothelin corresponds to standard big endothelin (porcine, 1-39). These results suggest that aortic strips with endothelium release endothelin and big endothelin slowly but continuously into the extracellular space and that these releases can be stimulated by thrombin.