UREMIC TOXIC RETENTION SOLUTES DEPRESS POLYMORPHONUCLEAR RESPONSE PHAGOCYTOSIS

Previous studies from our laboratory have demonstrated that the activi ty of the hexose monophosphate shunt (HMS) pathway in phagocytosis-rel ated respiratory burst is disturbed in end-stage renal disease. To det ermine whether uraemic solute retention is responsible for this defect the HMS-path was evaluated by measurements of glucose-1-C-14 utilizat ion and determination of (CO2)-C-14, production in polymorphonuclear c ells (PMNLs), suspended in normal plasma or uraemic biological fluids. Normal PMNLs, while suspended in normal or uraemic plasma, were stimu lated with either latex, zymosan or Staph. aureus; CO, generation (mea sured as DPM/10(3) PMNL, normal versus uraemic plasma) was depressed i n uraemic plasma in response to latex (from 43 +/- 5 to 20 +/- 3), zym osan (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 inhibiti on was similar for each stimulus. To characterize the substances respo nsible for this defect we fractionated uraemic plasma ultrafiltrate by polarity-based semipreparative C,, reversed phase HPLC and found a de creased 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 t wo 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 activi ty related to phagocytosis, and that at least two groups of components with different characteristics are involved.