In isolated working rat hearts we have evaluated the effects of preconditioning on postischemic coronary endothelial permeability. Isolated Wistar male rat hearts were used and subdivided into three groups: Group A, control hearts submitted to 20 min global normothermic
ischemia; Group B, hearts subjected, before
ischemia, to preconditioning (three phases of 3 min
ischemia, each one followed to 2 min Langendorff reperfusion; Group C, hearts submitted to preconditioning and hypertonic reperfusion (by adding 80 mM
sucrose to normal perfusion
buffer), in order to increase the effects on postischemic interstitial fluid accumulation (osmotic forces balance). A 65 min working heart reperfusion was also performed to assess functional response. We have evaluate the hemodynamic changes (coronary and aortic flows, systolic aortic pressure, work minute), reperfusion arrhythmias, heart weight changes (ww/dw), myocardial
enzyme release (
creatine phosphokinase and lactic
dehydrogenase) and microcirculation permeability changes (
FITC.albumin diffusion), as an index of endothelial function. In Group B, a significant reduction of
ischemia-
reperfusion damage (functional recovery,
enzyme release and arrhythmias) was detected with respect to Group A. In Group C this reduction was significantly more evident with respect to groups A and B. In Groups B and C, a significant reduction in myocardial reperfusion (ww/dw: A: 5.9 +/- 0.5, B: 4.9 +/- 1.1, p < 0.02 vs A, C: 4.4 +/- 0.6, p < 0.01 vs A)
edema and
FITC-albumin diffusion (A: 32.8 +/- 5.9% area; B: 16.3 +/- 6.1% area, p < 0.01 vs A; C: 13.3 +/- 4.5% area, p < 0.01 vs A), especially in perimyocytic space was also observed. Data show that preconditioning may exert a cardioprotective effect by reducing endothelial postischemic functional alterations (vascular permeability) and reperfusion
edema. The importance of fluid diffusion within the interstitium in the development of
reperfusion damage is supported by better postischemic recovery in Group C, in which an interference on osmotic load was performed.