Cardioprotective effect of diazepam on ischemia-reperfused isolated hyperthyroid rat heart

Hyperthyroidism increases the vulnerability of the heart to ischemia-reperfusion (I/R) injury. Regarding the fact that diazepam also aff ects cardiac I/R injury, the current study was conducted to investigate the eff ect of diazepam on ischemia-reperfused isolated hyperthyroid rat heart. Th e animals were divided into 6 groups: the control, hyperthyroid, control diazepam (1 mg/kg), hyperthyroid diazepam (1 mg/kg), control diazepam (5 mg/kg), and hyperthyroid diazepam (5 mg/kg) groups. Langendorff -perfused rat hearts underwent 40 min of global ischemia and 45 min of reperfusion. Diff erent cardiac parameters, including the left ventricular developed pressure, heart rate, coronary fl ow, and rate pressure product (RPP), were measured. Lactate dehydrogenase (LDH) release was determined in reperfusion to evaluate the severity of the myocardial injury. Th e results showed that the RPP recovery percentage signifi cantly decreased in the hyperthyroid group compared with control group, whereas comparison of the hyperthyroid diazepam (1 mg/kg) with the control and control diazepam (1 mg/kg) groups did not reveal a signifi cant diff erence. Th ese results were confi rmed by LDH test, demonstrating that administration of diazepam (1 mg/kg) protected the heart against I/R injury in the hyperthyroid group and signifi cantly decreased the I/R injury, which was probably due to the function of diazepam as a phosphodiesterase 4 inhibitor.