Postconditioning in females depends on injury severity

Background. Postconditioning, a series of brief ischemia/reperfusion (I/R) cycles at reperfusion onset, is a recently described novel approach to attenuate I/R injury, and because it is an after-injury treatment strategy, it may have greater clinical potential than preconditioning. However, it has not been determined whether postconditioning is effective in women. Materials and methods. Adult male and female (250300 g) Sprague-Dawley rat hearts (n = 25) were isolated, perfused via Langendorff model, and subjected to 15 min of equilibration, 20 or 25 min of global index ischemia (37 degrees C), and 40 min total reperfusion. Postconditioned hearts were subjected to 6 cycles of 10-s reperfusion/10-s ischemia immediately after release of the global index ischemia. Hearts were assigned randomly to one of four groups: 1) control hearts, 20 min index ischemia; 2) postconditioned hearts, 20 min index ischemia; 3) control hearts, 25 min index ischemia; or 4) postconditioned hearts, 25 min index ischemia. All data are reported as mean +/- SEM and were analyzed with unpaired student's t test; P < 0.05 considered significant. Results. Postconditioning in female rats after 20 min of ischemia reduced depression of left ventricular developed pressure (93.9 +/- 6.7% postconditioning recovery versus 58.6 +/- 12.6% control recovery, P < 0.05), attenuated the increase of end-diastolic pressure (P < 0.05), and reduced the depression of +dP/dT and -dP/dT (P < 0.05). The postconditioning protective effect disappeared in female rats exposed to 25 min of ischemia. The postconditioning protective effect was observed in male rats after both 20 min and 25 min ischemia. Conclusions. Postconditioning confers cardioprotection in leukocyte-free, buffer-perfused female hearts, but this protection may depend on ischemia duration. The attractive potential for the clinical application of postconditioning, however, warrants further studies to elucidate the mechanistic pathways and differences in males and female rats. (c)(c) 2006 Elsevier Inc. All rights reserved.