Systemic responses in patients with intermittent claudication after treadmill exercise.

The effect of 5 min treadmill exercise was investigated in claudicant patients and healthy controls; systemic neutrophil count, plasma thromboxane and von Willebrand's factor (a marker for endothelial injury) were measured. Median (interquartile range (i.q.r.)) resting neutrophil count was 5.6 (5.2-6.0) x 10(6) cells l-1 in claudicants and 2.8 (2.6-3.2) x 10(6) l-1 in controls (P < 0.05); this increased in those with claudication to 7.1 (6.2-7.7) x 10(6) l-1 immediately after exercise (P < 0.05). The resting plasma thromboxane level was 32.1 (25.0-60.0) pg ml-1 in claudicants and rose to 135.0 (104.0-141.3) pg ml-1 15 min after exercise, compared with a rise from 25.0 (22.0-33.5) to 55.5 (33.0-67.0) pg ml-1 in controls (P < 0.05). The resting serum von Willebrand's factor level was 127 (110-135) units dl-1 in claudicants compared with 60 (48-71) units dl-1 in controls; this difference persisted after exercise (P < 0.01). In patients with claudication, the level of von Willebrand's factor increased to 150 (140-156) units dl-1 60 min after exercise (P < 0.05). Free radical scavenging capacity was also investigated by measuring the plasma antioxidant activity of glutathione peroxidase and its essential non-metal cofactor selenium. Scavenging capacity was lower in claudicant patients whose median (i.q.r.) glutathione peroxidase activity (change in absorbance per min per ml plasma) was 2.84 (2.39-3.61) versus 3.24 (3.06-3.79) in controls (P < 0.05). Similarly, plasma concentrations of selenium were lower in claudicants at a median (i.q.r.) of 75.0 (58.0-81.0) micrograms l-1 compared with 88.0 (75.0-92.5) micrograms l-1 in controls (P < 0.05). Exercise in claudicant patients leads to neutrophilia and thromboxane production with subsequent endothelial injury. The antioxidant activity of glutathione peroxidase is reduced in patients with claudication and may allow the unopposed action of free radicals to damage endothelium.