Studies of miR-21 regulation in wiltype and <i>Per2</i>^<i>-/-</i> mice after cardiac ischemic preconditioning.

<p>Wildtype (<b>A</b>) or <i>Per2</i>^<i>-/-</i> mice (<b>B</b>) were exposed to cardiac IPC, consisting of 4 x 5 minutes of ischemia followed by 5 minutes of reperfusion each, followed by a final reperfusion time of 120 min. Heart tissue was snap-frozen with clamps pre-cooled to the temperature of liquid nitrogen. Total RNA was isolated from murine heart tissue using Qiazol Reagent and separated into mRNA and miRNA components following manufactures instructions (SA-Biosciences, Qiagen). cDNA from miRNA was generated using miScript RT II kits (Qiagen) and transcript levels were determined by real-time RT-PCR (iCycler; Bio-Rad Laboratories Inc.; mean±SD, n = 3).