Myocardial Function of Hyperthyroid Rats in Presence of Diazepam in Langendorff Setup

Background: Modulation of Ischemia-Reperfusion (I/R) injury is highly important in medicine, especially in hyperthyroidism condition. The effect of diazepam as a benzodiazepine on cardiac I/R injury is also clinically important. The chronic effect of diazepam in this case has been reported previously. Objectives: This study aimed to investigate the effect of acute diazepam perfusion on isolated heart of hyperthyroid rats during I/R. Materials and Methods: Male rats (n = 32, weighing 250 - 300 gr) were randomly divided into 4 groups: control, hyperthyroid, control diazepam perfused, and hyperthyroid diazepam perfused. Isolated hearts were perfused through Langendorff method. Four sets of data were collected at baseline (20 minutes), diazepam perfusion (10 minutes, 100 µmol/L), ischemia (40 minutes), and reperfusion (45 minutes) periods. Cardiac parameters, including Left Ventricular Developed pressure (LVDP; mmHg) and Rate Pressure Product (RPP; mmHg × beats/min) were measured, as well. Lactate dehydrogenase (LDH; mU/mL) was also assessed for evaluation of I/R injury. The data were analyzed using ANOVA and Student t-test and P < 0.05 was considered as statistically significant. Results: RPP significantly declined in the hyperthyroid group after diazepam perfusion compared to the baseline (24046 ± 1381 versus 18269 ± 711, P = 0.012, 95% CI: 1724 - 9828). Besides, RPP and LVDP significantly increased in the hyperthyroid diazepam perfused group compared to the hyperthyroid group at the end of the reperfusion period (12469 ± 1422 versus 4007 ± 258, P < 0.001, CI: 5066 - 11856 and 47 ± 2.8 versus 23 ± 2.8, P < 0.001, CI: 11-35, respectively). These findings were confirmed by LDH levels (19.08 ± 1.06 versus 41.07 ± 8.14, P = 0.002, CI: -34.4 - -9.4-35). Conclusions: The results showed that acute diazepam perfusion to isolated hyperthyroid rats’ hearts could significantly improve cardiac function following ischemia and protect the heart against I/R injury.