The differential extraction and immunoluminometric assay of Urotensin II and Urotensin-related peptide in heart failure

Abstract

Urotensin II (UTN) is a cyclic eleven amino acid peptide that can induce endothelial independent vasoconstriction and endothelial dependent vasodilatation in human vasculature. The cyclic part of the peptide is composed of six amino acids. Similarly, Urotensin Related Peptide (URP) is only eight amino acids long but shares the identical ring structure to UTN. Plasma UTN has been shown to be raised in patients with chronic heart failure (CHF) suggesting a potential role of the peptide system in the pathophysiology of heart failure. Given their similar structures, techniques measuring plasma UTN may also be simultaneously detecting URP and could provide a misrepresentation of true UTN and URP levels in patients’ plasma. Thus we describe the development of a solid phase extraction technique that can differentially extract UTN and URP from human plasma so that they can be assayed separately using non-radioactive immunoluminometric assays. This reliable and sensitive protocol was utilized to characterise the plasma of 20 healthy controls and 20 patients admitted with acute heart failure (AHF). The groups were age and sex matched. Plasma UTN was significantly raised in patients with AHF on admission when compared to controls (median 1.29 [range 0.50–5.55]pmol/L vs 0.50 [0.50–3.33]pmol/L, p=0.019). Likewise plasma URP was significantly higher in the heart failure group on admission (8.38 [1.30–66.80]pmol/L vs 2.25 [1.30–14.40]pmol/L, p<0.005). This suggests a role for both members of the Urotensin peptide system in acute heart failure.