Serum levels of pigmentation markers are elevated in patients undergoing hemodialysis

Background: Diffuse hyperpigmentation is common among patients with chronic renal failure undergoing hemodialysis (HD). We have examined serum levels of 5-S-cysteinyldopa (5SCD, a pheomelanin precursor), pheomelanin, eumelanin, and protein-bound (PB-) 3,4-dihydroxyphenylalanine (DOPA) and PB- 5SCD in HD patients. Methods: Pheomelanin and eumelanin were assayed by chemical degradation methods. Results: Serum levels of free 5SCD in HD patients (n = 16) were 9-fold higher than in healthy controls (n = 16). Levels of pheomelanin in HD patients were 2.6-fold higher than in controls, while levels of eumelanin did not differ between HD patients and controls. Levels of PB- DOPA and PB- 5SCD in HD patients were approximately 1.5-fold higher than in controls. Serum levels of free 5SCD were positively correlated to the duration of HD therapy. Conclusions: The high constitutive levels of free 5SCD, pheomelanin, and PB-DOPA in the blood may be deteriorating in HD patients through the production of reactive oxygen species.