Plasma inhibitors of the erythrocyte hexose monophosphate shunt in uraemia.

Sulphaemoglobin production, induced by an oxidative stress (ascorbate and cyanide) has been studied in uraemic patients. Results are expressed as the ratio of optic density of sulphaemoglobin (620nm) to optic density of total haemoglobin (540nm). The mean (+/- SEM) ratio found was 0.35 +/- 0.03 in 28 controls and 0.56 +/- 0,03 in 51 uraemic subjects (p less than 0.001). Cross incubation tests demonstrated that the anomaly was caused by a plasma factor. In vitro studies - guanidinic compounds added to control erythrocyte suspensions before incubation - suggest that this factor might be guanidinic propionic acid.