Abstract
Previously, we have demonstrated a late phase protection of ischemic preconditioning in the microcirculation of cremaster muscle. This microvascular protection was blocked by a non‐specific NOS inhibitor. The purpose of present study was to evaluate endothelial function in the terminal arteriole of cremaster muscle after 24‐h of ischemic preconditioning followed by 4‐h warm ischemia and to evaluate eNOS and iNOS gene and protein expression at 24 h after ischemic preconditioning in the cremaster muscle. A vascular pedicle isolated cremaster muscle in male SD rats underwent 45‐min of ischemic preconditioning and 24 h later, 4‐h of warm ischemia followed by reperfusion. Endothelial‐dependent and ‐independent vasodilatation was evaluated on day 2 after 4‐h ischemia and 60‐min of reperfusion. Cremaster muscles were harvested at 24 h after ischemic preconditioning for measuring of eNOS and iNOS gene expression by reverse transcriptase polymerase chain reaction (RT‐PCR) and protein expression by western blotting analysis. We found that IPC significantly attenuated endothelial dysfunction induced by 4‐h warm ischemia and reperfusion. The expression of eNOS and iNOS mRNA shown a 229% and 135% increase respectively in IPC treated cremaster muscles as compared to normal cremaster muscles (P < 0.05). The expression of eNOS and iNOS protein exhibited a 133% and 148% increase respectively in IPC treated cremaster muscles as compared to normal cremaster muscles (P < 0.05). There was no statistically significant difference between normal cremaster muscle and sham IPC treated cremaster muscle. The results suggest that IPC preventing vascular endothelial dysfunction from ischemia/reperfusion injury may be due to the enhanced NOS expression. These results combined with the results from our previous studies suggest that IPC‐induced microvascular protection in the skeletal muscle may act through a NOS‐dependent mechanism. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.