Submitted on April 7, 2004
Accepted on May 26, 2004
Reperfusion injury in skeletal muscle is reduced in inducible nitric oxide synthase knockout mice
Wen-Ning Qi1, Long-En Chen1*, Li Zhang1, Jerry P Eu2, Anthony V Seaber1, and James R Urbaniak1
1 The Orthopaedic Microsurgery Laboratories, Department of Surgery, Duke University, Durham, NC, USA
2 Pulmonary Divisions, Department of Medicine and Department of Cell Biology, Duke University, Durham, NC, USA
* To whom correspondence should be addressed. E-mail: chen0006{at}mc.duke.edu.
Inducible nitric oxide synthase (iNOS) participates in many pathological events, and selective inhibition of iNOS has been shown to reduce ischemia/reperfusion (I/R) injury in different tissues. To further confirm its role in this injury process, I/R injury was observed in denervated cremaster muscles of iNOS deficient (iNOS-/-) and wild-type mice. After 3-hr ischemia and 90-min reperfusion, blood flow in reperfused muscle was 80±8.5% (mean ± SE) of baseline at 10-min reperfusion and completely returned to the pre-ischemia baseline after 20 min in iNOS-/- mice. In contrast, blood flow was 32±7.4% at 10 min and increased to 60±20% of the baseline level at 90 min in wild-type mice (p<0.001 vs. iNOS-/- mice at all time points). The increased muscle blood flow in iNOS-/- mice was associated with significantly less vasospasm in all three sizes of arterial vessel size categories. The weight ratio to the contralateral muscle not subjected to I/R was greater in wild-type mice (173±11%) than in iNOS-/- mice (117±3%) (p<0.01). Inflammation and neutrophil extravasation were also more severe in wild-type mice. Western blot analysis demonstrated an absence of iNOS protein band in iNOS-/- mice and upregulation of iNOS protein expression in wild-type mice. Our results have confirmed the importance of iNOS in I/R injury. Upregulated iNOS exacerbates I/R injury and appears to be a therapeutic target in protection of tissues against this type of injury.
