The isolated blood‐perfused rat heart: an inappropriate model for the study of ischaemia‐ and infarction‐related ventricular fibrillation

Abstract

1 Well-characterized in vivo and in vitro models exist for the study of ischaemia-and infarctionrelated ventricular ®brillation (VF). In rats in vivo, VF appears to occur in distinct acute ischaemia-(early) and infarction-related (late) phases. Interestingly, isolated buer-perfused rat hearts do not develop late VF. This raises the possibility that unidenti®ed components of the blood may be responsible for late VF. We thus sought to characterize an isolated blood-perfused rat heart in order to investigate the possible in¯uence of blood components on arrhythmias arising from ischaemia and infarction. 2 Hearts, excised from male Wistar rats, were perfused in the Langendor mode with blood from support rats (male Wistar, 350 ± 430 g) via an extracorporeal circuit. Perfused hearts underwent left coronary artery occlusion for 240 min or a sham procedure (n=10 group 71). 3 Only 10% of ischaemic hearts developed late VF (90 ± 240 min). Tissue myeloperoxidase activity (an index of neutrophil accumulation) increased during ischaemia from 0.017+0.004 (six fresh hearts) to 0.056+0.005 units mg protein 71 (P50.05) at 240 min, but values were similar in sham hearts (0.083+0.013). Likewise, the decline (71 vs 240 min of ischaemia shown) in circulating total white blood cells from 6.8+0.5 to 1.9+0.2610 3 ml 71 and in platelets from 441+32 to 274+16610 3 ml 71 (both P50.05) was similar in time-matched sham hearts (data not shown). 4 Surprisingly, only 10% of ischaemic hearts developed early VF (0 ± 90 min), although the incidence of early ventricular tachycardia was 100% in these hearts (P50.05 vs sham hearts). Blood K + values were normal (hyperkalaemia suppresses VF). 5 Although late VF was absent in blood-perfused hearts, it would be premature to conclude from this that late VF is not mediated by blood components. This is because the similar neutrophil accumulation in ischaemic and sham hearts, the decline in numbers of circulating blood components, and the unexpected paucity of early VF all question the validity of the model.

Langendorff's isolated perfused rat heart technique: a review

“…The volume of blood needed (perfusing one rat heart would require the blood of several rats), the inability to use of blood from some (but not all) larger species because they have larger erythrocytes than the rat and cannot traverse rat heart capillaries and the difficulty in oxygenating the blood since conventional gassing creates extensive foaming and damage to blood cells. 7,29,30 Temperature plays very important role in isolated perfused heart experiment. There is a strong relationship in between cardiac contractile function and temperature.…”

Gene and protein expression changes in response to normoxic perfusion in mouse hearts

“…As the present study was performed in crystalloid-perfused isolated mouse hearts and the analysis of gene expression was done using cardiac tissue that did not contain components of blood, cellular regulatory pathways might be somewhat different in the present ex vivo experimental model as compared to in vivo situations. Perfusion with blood might solve this issue, however, blood perfusion can be a problem in itself (Clements-Jewery et al, 2002). In our present studies, to avoid spontaneous occurrence of arrhythmias, we used a perfusion buffer containing high potassium.…”

“…It is a relatively simple model and it provides a highly reproducible preparation which can be used for comprehensive examinations of cardiac contractile function, electrophysiology, cellular biochemistry and molecular biology. However, the major limitations of this model include deterioration of myocardial function within beyond 60 min possibly due to oxidative and nitrosative stress (Ferdinandy, Panas, & Schulz, 1999) and unusual appearance of cardiac arrhythmias (Clements-Jewery, Hearse, & Curtis, 2002;Curtis, 1998;Hearse, Richard, Yellon, & Kingma, 1988;Miyashita et al, 2000;Ravingerova, Pancza, Ziegelhoffer, & Styk, 2005;Schomisch et al, 2005). Although the most frequently used ex vivo heart preparation is the rat heart, due to the lower cost and the appearance of the genetically modified mice, ex vivo mice heart preparations have been rapidly spreading in the scientific community.…”

Cardioprotective efficacy of zoniporide, a potent and selective inhibitor of Na+/H+ exchanger isoform 1, in an experimental model of cardiopulmonary bypass

“…The effects of hypothermic cardioplegic arrest and subsequent normothermic reperfusion on myocardial viability and function were assessed, in the absence or presence of zoniporide treatment, using an isolated blood-perfused heart preparation, which we have described in detail previously Sutherland & Hearse, 2000;Clements-Jewery et al, 2002). Medical Ltd), and maintained for 10 min prior to aortic cannulation of the donor heart.…”

“…MPO (MPO) activity in myocardial tissue samples was measured, as an index of neutrophil accumulation, using methodology that we have described in detail previously (Clements-Jewery et al, 2002). In brief, the tissue samples were homogenized in 0.5% hexadecyltrimethylammonium bromide (HETAB) in 50 mM potassium phosphate buffer (pH 6), in the ratio 1 ml HETAB/100 mg tissue.…”