Ascorbate-cyanide test on red blood cells in uremia: effect of guanidinopropionic acid.

Red blood cells (RBC) of uremic or control subjects have been exposed to an oxidative stress by ascorbate and cyanide. The spectrophotometric determination of the sulfhemoglobin production has been used as a reliable method for the measurement of the hexose monophosphate shunt. The sulfhemoglobin production by RBC was significantly higher in uremic than in control subjects. Uremic plasma increased this production in uremic as well as in control RBC while control plasma was ineffective under the same conditions. In vitro the guanidinopropionic acid had the same toxic effect on normal RBC. These results suggest that the abnormal sulfhemoglobin production by uremic RBC might be due to an increased plasma concentration of guanidinopropionic acid in uremia.