Nitric oxide involvement in reperfusion injury of denervated muscle.

Purpose: To investigate whether inhibition of inducible nitric oxide synthase (iNOS) improves microcirculation in denervated and reperfused skeletal muscle.

Methods: The cremaster muscles of 52 rats received iNOS inhibitor 1400W (3 mg/kg) or phosphate buffered saline (PBS) and underwent either 3 hours of ischemia and 1.5 hours of reperfusion or a sham operation. During reperfusion the vessel diameters were measured by using intravital videomicroscopy and overall muscle blood flow was measured with laser Doppler flowmetry. The expression of NOS messenger RNA (mRNA) and protein was determined by using real-time reverse-transcription polymerase chain reaction and Western blot, respectively.

Results: 1400W treatment significantly increased the mean blood flow of the reperfused muscle compared with controls, and this was associated with significantly less vasospasm in 10 to 20 microm, 21 to 40 microm, and 41 to 70 microm arterioles. The expression of iNOS mRNA and protein in controls increased 23-fold and 6-fold from normal, respectively, but was reduced to only a 2-fold increase in the 1400W-treated muscles. The ischemia/reperfusion (I/R)-induced decrease of endothelial NOS (eNOS) and neuronal NOS (nNOS) expression in controls was not significantly changed after 1400W treatment.

Conclusions: Our data support a nitric oxide-mediated mechanism in reperfusion injury and show the importance of inhibition of iNOS in reducing reperfusion injury in denervated skeletal muscle. Our results suggest potential benefits via inhibition of iNOS to improve clinical outcomes not only for hand surgeons who work in the microsurgery field, but also for other physicians whose work involves ischemia/reperfusion injury.