INCREASED PHAGOCYTIC CAPACITY OF THE BLOOD, BUT DECREASED PHAGOCYTIC-ACTIVITY PER INDIVIDUAL CIRCULATING NEUTROPHIL AFTER AN ULTRADISTANCE RUN

The effect of a long strenuous endurance exercise on the phagocytic fu nction of neutrophils was examined. 9 athletes [7 males, 2 females, ag e: 36-68 years, body mass: 64 (SD 10) kg, height: 175 (SD 10) cm] comp leted a competetive 100 km run in 8:07 (median value; range: 7:29-9:50 hours). In a whole blood assay the phagocytosis of opsonized E. coli, the receptor density of the Fc gamma receptor 3 (CD16) and the comple ment receptor 3 (CD11b, direct immunofluorescence) of neutrophils were measured on a per cell basis by flow cytometry before and up to 3 hou rs after the race. The phagocytic rate (percentage of neutrophils inco rporating bacteria) was unchanged after exercise, whereas the phagocyt ic activity (number of incorporated bacteria per cell) was significant ly reduced by -34 (SD 8) % (Wilcoxon test, P<0.001). The total phagocy tic capacity of the blood increased 2-3fold post exercise. The surface antigen expressions of CD11b and CD16 were unaffected by the ultradis tance run. The results indicate either a reduced phagocytic function o f neutrophils on a single cell basis or the mobilization of neutrophil s of the marginal pool with a lower phagocytic activity. However, afte r a long endurance exercise the phagocytotic capacity of the blood was enhanced due to increased cell concentrations.