Prolonged effect of leukocytosis on reperfusion injury of rat intestine: real-time ATP change studied using (31)P MRS.

The intestine is one of the most sensitive tissues to ischemia and reperfusion (I/R). Polymorphonuclear neutrophils (PMN) may play an important role in ischemic injury. (31)P magnetic resonance spectroscopy (MRS) has been used to continuously monitor the energy metabolism of an animal in situ. We have applied MRS to study the effect of PMN on the I/R injury of rat intestine. In a rat model of 30 min of intestinal ischemia and reperfusion, the number of PMNs was manipulated: group A, control; group B, leukopenia induced by cyclophosphamide; group C, leukocytosis induced by granulocyte colony-stimulating factor (G-CSF). MRS was employed to measure the level of real-time intestinal ATP and pH in vivo. In group A, ATP rapidly recovered on reperfusion to 61.0 +/- 11.0% of the preischemia level and maintained that level during reperfusion. The other two groups showed similar recovery of ATP at the initial phase of the reperfusion (<10 min). ATP in group B continued to recover, reaching 74.0 +/- 10.0% of the preischemia level. After the initial recovery, ATP in group C deteriorated reaching 46.0 +/- 4.4% of the preischemic level at 150 min of reperfusion. In group A and group B tissue pH decreased on ischemia and recovered on reperfusion in a similar manner. In group C, tissue pH was significantly lower than in other groups during I/R. Leukocytosis induced by G-CSF exerts a prolonged effect on ATP during I/R and leukocyte depletion helps protect against the I/R injury.