Previous studies from our laboratory have demonstrated that the activity of the hexose monophosphate shunt (HMS) pathway in phagocytosis-related respiratory burst is disturbed in end-stage renal disease. To determine whether uraemic solute retention is responsible for this defect the HMS-path was evaluated by measurements of glucose-1-C14 utilization and determination of 14CO2 production in polymorphonuclear cells (PMNLs), suspended in normal plasma or uraemic biological fluids. Normal PMNLs, while suspended in normal or uraemic plasma, were stimulated with either latex, zymosan or Staph. aureus; CO2 generation (measured as DPM/10(3) PMNL, normal versus uraemic plasma) was depressed in uraemic plasma in response to latex (from 43 +/- 5 to 20 +/- 3), zymosan (from 72 +/- 8 to 47 +/- 4) (P < 0.01), and Staph aureus (from 73 +/- 17 to 47 +/- 8 DPM/10(3) PMNL) (P < 0.05). The degree of inhibition was similar for each stimulus. To characterize the substances responsible for this defect we fractionated uraemic plasma ultrafiltrate by polarity-based semipreparative C18 reversed phase HPLC and found a decreased response to Staph. aureus in the presence of fraction 2 (from 102 +/- 13 to 23 +/- 10 DPM/10(3) PMNL, P < 0.05), and in fractions 8 and 11 (lowest value in fraction 8, 54 +/- 14 DPM/10(3) PMNL, P < 0.05 versus control). The pattern of HPLC elution on a gradient from 100% formiate (pH 4.0) to 100% methanol indicates that there are at least two chemically distinguishable groups of compounds, one hydrophilic (in fraction 2), and one lipophilic (in fractions 8 and 11). We conclude that uraemic biological fluids contain factors that inhibit HMS activity related to phagocytosis, and that at least two groups of components with different characteristics are involved.