Immunoreactive endothelin in urine of patients with and without diabetes mellitus

Immunoreactive (ir)-endothelin (ET) in urine was studied with a radioimmunoassay in patients with diabetes mellitus (DM) and non-DM diseases including endocrine disorders, primary glomerular diseases, autoimmune diseases, and hematological malignancies. Twenty-four-hour excretions (mean +/- SEM) of ir-ET were 8.0 +/- 0.9 pmol/day in the DM group (n = 13) and 9.5 +/- 1.2 pmol/day in the non-DM group (n = 51). No significant differences among DM and other disease groups were noted with respect to 24-h ir-ET excretion. Reverse-phase high-performance liquid chromatography of a normal urine extract revealed a major peak eluting later than ET-1. Gel chromatography revealed a single major peak in a smaller molecular weight (MW) region in normal urine and an additional peak in larger MW region in a urine extract from a DM patient. Urinary ir-ET consists of at least two components which may be metabolites of ET or ET precursors in plasma or peptides derived from the kidney.