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 affects cardiac I/R injury, the current study was conducted to investigate the effect of diazepam on ischemia-reperfused isolated hyperthyroid rat heart. The 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. Different cardiac parameters, including the left ventricular developed pressure, heart rate, coronary flow, and rate pressure product (RPP), were measured. Lactate dehydrogenase (LDH) release was determined in reperfusion to evaluate the severity of the myocardial injury. The results showed that the RPP recovery percentage significantly 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 significant difference. These results were confirmed by LDH test, demonstrating that administration of diazepam (1 mg/kg) protected the heart against I/R injury in the hyperthyroid group and significantly decreased the I/R injury, which was probably due to the function of diazepam as a phosphodiesterase 4 inhibitor.