Session P87.3

Model of Preconditioning in Guinea Pig and Rabbit Isolated Hearts Loaded with Voltage-Sensitive Dye Di-4-ANEPPS

K Fialova*, J Kolárová, I Provaznik, M Novakova

Masaryk University
Brno, Czech Repub.

Myocardial ischemia and reperfusion phenomena have been studied repeatedly in various models. The aim of this study was to verify preconditioning model in guinea pig and rabbit Langendorff-perfused hearts loaded with voltage-sensitive dye (VSD) di-4-ANEPPS which we use to record monophasic action potentials (MAPs) by optical method. The heart was perfused according to Langendorff at constant pressure (80mmHg) with Krebs-Henseleit solution (K-H, 37° C, 1.25mM Ca2+). Each experiment consisted of heart isolation, control perfusion, dye loading, washout and MAPs recording. In our previous experiments, we have observed and consequently studied specific electrophysiological changes during the procedure of VSD loading and washout in both species. These changes were more expressed in guinea pig myocardium, thus we started to use rabbit hearts for most of our experiments with VSD. Nevertheless, design and verification of our model for studying the preconditioning phenomenon was needed, since little is known about putative modification of this experimental model by di-4-ANEPPS. The hearts of three guinea pigs and seven New Zealand rabbits were included in this study. All hearts underwent the same procedure as described above. Then, MAPs were recorded by optical probe, 3D-electrogram by touch-less method and mean coronary flow by collecting the perfusate. The model of preconditioning consisted of three successive periods of global (flow) ischemia followed always by reperfusion phase. In guinea pig, ischemia lasted 5 minutes and was followed by 15 minutes of reperfusion, in rabbits – each phase of preconditioning protocol took 10 minutes. The recorded electrograms were stored for off-line processing. The incidence of arrhythmias in particular periods was assessed according to Lambeth score. Typical changes of electrogram shape (ST elevation) were observed from the beginning of ischemia in guinea pig hearts. However, these changes were quite robust and accompanied by numerous premature ventricular beats (score 2). It was the reason for ischemia of short duration. Moreover, we did not observe clear attenuation of these electrogram changes during the second and the third ischemic period. On the contrary, in rabbit hearts the typical ischemic changes in electrogram were also present, together with a few arrhythmias (score 1) and were diminished during consecutive ischemic periods. Rabbit hearts loaded with VSD tolerated ischemia of longer duration without severe alterations of electrogram. Although the procedure of dye loading affects electrophysiological properties of the myocardium, in case of rabbit heart it is negligible (it is quite resistant to side-effects of VSDs). In guinea pig myocardium, more cautiousness is needed. Supported by GACR 102/07/1473, GACR 102/07/P521, MSM 0021622402.

(Abstract Control Number: 169)