Red cell metabolism in renal failure--the effect of dialysis.

The mechanism of the increased haemoglobin (Hb) and erythrocyte survival in continuous ambulatory peritoneal dialysis (CAPD) compared to haemodialysis (HD) was investigated by measuring hexose monophosphate shunt (HMP) activity and reduced glutathione concentration (GSH) in 12 patients--six patients who were stable on CAPD, and six patients who were stable on HD, and also six normal controls. We confirmed the rise in haemoglobin in the CAPD group. The HMP activity, measured by the liberation of 14CO2 from radioactive glucose labelled at the C1 position shows that both HD and CAPD groups fall into the normal range (normal 3-11%) although the HMP activity is higher in the HD group. The reduced glutathione concentration in the three groups was: normal controls 2.41 +/- 0.19 mmol/l; HD 3.31 +/- 0.43 mmol/l; CAPD 2.68 +/- 0.24 mmol/l. The HD group is significantly higher (P less than 0.01) than both normal and CAPD. We conclude that the rise in haemoglobin in CAPD patients is not related to a more effective HMP. This suggests other mechanisms i.e. marrow function or red-cell loss in HD may be the reason for the lower haemoglobin in this group.