Rat strain differences in flap tolerance to ischemia

The rat epigastric island flap model is commonly used to explore ischemia-related phenomena. We sought to evaluate strain differences in tolerance to ischemia using two commonly used rat strains: Sprague-Dawley and Lewis. Epigastric flaps (3 x 6 cm) based on the superficial epigastric artery and vein were raised bilaterally in each rat (2 flaps/rat). Ischemia was induced for 10,12,14, or 16 hours by placing temporary occlusion clamps on each vessel of the vascular pedicle. Surviving flap areas were assessed planimetrically after 7 days. The average area of surviving flap tissue was greater in the Lewis rats for all ischemia times; this achieved significance for 12 hours and 14 hours of ischemia (P < 0.005). These findings indicate that comparisons among studies on rat flap ischemia must take into account the particular strain used. Furthermore, these findings suggest an inherent capacity of Lewis rat tissue to withstand ischemia better than tissue of the Sprague-Dawley rat strain.