Introduction: It has been suggested that extracts from grapes or berries such as blueberries are beneficial and protective against cardiovascular diseases, probably due to a high content of polyphenols like anthocyanins. Anthocyanins have several effects, for instance, being antioxidants and stimulate nitric oxide production. They are water-soluble, low-molecular size substances (molecular weight 4-500) and thus easily transverse cell membranes.
Hypothesis: Pre-treatment with a blueberry extract containing 80% anthocyanins protects against ischemia-reperfusion injury.
Methods: Rats were randomized into 4 groups and pretreated 2-3 weeks with blueberry extracts (Medox®, Medpalett, Sandnes, Norway) dissolved in their drinking water (approximately 0.7, 7, or 70 mg daily). Controls drank regular tap water. The hearts were harvested and retrogradely perfused, undergoing 30 minutes of global ischemia and 120 minutes of reperfusion. Infarct size as well as left ventricular pressures, coronary flow, and heart rate were measured.
Results: All three groups receiving blueberry extract had lower heart rate during reperfusion (p=0.035). There was no difference between groups in cardiac function or infarct size (the group with the lowest extract dose had a non-important reduction of infarct size, p=0.27).
Conclusion: The blueberry extract reduced heart rate during reperfusion, but had no important effect towards ischemia-reperfusion injury of the isolated rat heart.