Microvascular preconditioning is not detectable by corrosion casting in the isolated perfused rat heart after 30 minutes of ischaemia

Abstract

Objective. Ischaemic preconditioning protects the myocardium from ischaemic injury and may also protect the vascular endothelium from the deleterious effects of ischaemia and reperfusion. We examined the possibility that ischaemic preconditioning might preserve the integrity of the coronary microcirculation following ischaemia and reperfusion. Methods. Isolated rat hearts were perfused in Langendorff mode for 30 minutes and then subjected to 30 minutes of global ischaemia with or without ischaemic preconditioning (three×three minute cycles). Some hearts underwent an additional 60 minutes of reperfusion. At the end of each protocol, microvascular corrosion casts were made by methylmethacrylate injection. Results. Median left ventricular capillary density [interquartile range] after ischaemia was slightly but not significantly better with preconditioning at 6.8 [4.0–14.7]×10−2 mm3.mg−1vs. 5.2 [2.6–7.1]×10−2 mm3.mg−1 (p =0.13). After 60 min of reperfusion, capillary density in preconditioned left ventricles was 20.7 [10.7–22.8]×10−2 mm3.mg−1vs. 16.0 [10.2–23.0]×10−2 mm3.mg−1 for untreated ventricles (p =0.47). Coronary blood flow and heart rate were unchanged from before ischaemia. Conclusions. Ischaemia for 30 minutes induced global left ventricular capillary loss which was unmodified by preconditioning. We did not demonstrate vascular preconditioning using this model.