P384 A new in vivo model of myocardial microcirculation during ischemia/reperfusion in mice.
1K.Knobloch, 1A.Lichtenberg, 1N.Khaladj, 1H.Schacht, 2S.Ringes-Lichtenberg, 1M.Pichlmaier, 1H.Mertsching, 1A.Haverich
1Thorax-, Herz- & Gefäßchirurgie, Medizinische Hochschule, Hannover; 2Kardiologie & Angiologie, Medizinische Hochschule, Hannover.

Myocardial ischemic/reperfusion (I/R) injury has been studied extensively in isolated Langendorff models, but in vivo data on parameters of microcirculation are limited. The mechanisms involved in myocardial I/R are activation of KATP-channels and modulation of several different adenosine receptor subtypes. We studied the effects of the KATP-channel opener rilmakalim (RI) on microcirculation in I/R in mice using a novel laser Doppler flowmetry and remission spectroscopy system (Oxygen-To-See“O2C”) and morphological evaluation using electron microscopy (EM).

16 mice with identical genetic backgrounds were randomized in two groups treated with RI vs. placebo. RI (0.5mg/kg-BW iv, n=8) was injected five minutes prior a 30min occlusion of the left anterior descending artery (LAD), followed by 30min of reperfusion with continous measurement of parameters of myocardial microcirculation in LAD area (myocardial oxygen saturation (SO2), postcapillary hemoglobin concentration (rHB), blood flow (BF)). Hearts were harvested after reperfusion and I/R damage was evaluated morphologically by EM.

Myocardial SO2 significantly decreased in ischemia in both groups (94 vs. 28%, RI: 95 vs. 23%, p<0.05) with consecutive increase over the reperfusion period (1min&15min: 28% vs. 62%, RI: 52 vs. 69%). rHb remained unchanged throughout I/R. Myocardial blood flow decreased in I/R significantly. EM evaluation revealed no quantitative differences between both groups concerning myocardial tissue injury.

Using oxygen-to-see, we could determine a decrease of SO2 in myocardial ischemia with consecutive increase during reperfusion without complete myocardial restitution. Despite the fact that rimakalim as a KATP-opener, administered five minutes prior myocardial infarction, has no significant positive effect on myocardial tissue microcirculation during I/R, this seems to be a promising model to evaluate in vivo parameters of microcirculation in mice.