Effect of urine component on leukocyte chemiluminescence response

In the urine, the function of polymorphonuclear leukocytes (PMNs) is thought to be impaired because of the high osmolality and low pH along with a high concentration of inorganic salts. We investigated the effect of the properties of urine and its components on the chemiluminescence (CL) response of PMNs. This was helped by using an artificial urine. The CL response was measured by automatic luminometer following stimulation of phorbol myristate acetate. We found the CL response of PMNs to be significantly suppressed at a pH of 6 or 5, but not suppressed at a pH of 7 or 8. The CL response was significantly reduced when the osmolality was increased to 580 or 800 mOsm/kg H2O by the addition of urea as compared to the response in the standard artificial urine at an osmolality of 425 mOsm/kg H2O. A change in the osmolality by the addition of mannitol only minimally influenced the CL responses. In addition, the CL response was significantly impaired by both low and high concentrations of sodium at 12 and 300 mEq/L as compared to 77.5 mEq/L in the standard artificial urine. Potassium significantly reduced the CL response in a concentration-dependent manner in the range of from 4 to 31 mEq/L as compared to 52.3 mEq/L in the standard artificial urine. A high concentration of calcium at 8.1 or 9.9 mg/dL reduced CL response as compared to 3.9 mg/dL, whereas CL response was not reduced by the change in the concentration of magnesium. A high concentration of creatinine significantly reduced the CL response as compared to the standard artificial urine. We conclude that the function of PMNs in urine is reduced mainly by urine pH, concentration of urea, sodium, potassium, and creatinine. We suggest that reversal of these change in urine may restore functions of PMNs to clear bacteria in patients with urinary tract infections.