The Eagle Biosciences Human Big Endothelin-1 ELISA Assay Kit in serum & plasma. The Eagle Biosciences Big Endothelin-1 ELISA Assay Kit is manufactured by Biomedica Gruppe and is for research use only, not to be used in diagnostic procedures. Sample Types: human serum or plasma (citrate, EDTA or heparin). Range: 0.1 - 3 pmol/L. Sensitivity: 0.02 pmol/L. Time: 5.5 hours ? Big Endothelin-1 (BigET) is a peptide of 38 amino acids and is the precursor of Endothelin-1 (ET), represented by amino acids 1-21. ET is a potent vasoconstrictor and is produced by vascular endothelial cells. Accordingly it has a wide tissue distribution. The cleavage of BigET by Endothelin Converting Enzyme (ECE) leads to ET and to a C?terminal fragment. Both BigET and ET are strong independent predictors of survival in patients with congestive heart failure, and identify a population with a very high risk mortality. The half-life of ET (1-21) in plasma is less than one minute, whereas clearance of BigET is much slower. BigET can therefore be determined more easily.