Fluorescent substances in uremic and normal serum

We measured the fluorescence, at various excitation (Ex) and emission (Em) wavelengths, of serum ultrafiltrates and fractions of serum resolved by chromatography on Sephadex G15, studying both normal subjects and patients in chronic renal failure requiring hemodialysis. We found hitherto undescribed fluorescence at Ex 380 nm/Em 440 nm and Ex 400 nm/Em 460 nm, the intensity being greatly increased in patients with chronic renal failure in comparison with normal subjects (p less than 0.005). This fluorescence persisted unaltered when serum was filtered through membranes having cutoffs ranging from 10 000 to 500 Da. Each serum fraction resolved by gel chromatography demonstrated a characteristic fluorescence, which was generally much more intense in uremics. The most intense fluorescence (Ex 380 nm/Em 440 nm and Ex 400 nm/Em 460 nm) was emitted in the higher-Mr fractions.