A simple reproducible model of free radical-injured isolated heart induced by 1,1-diphenyl-2-picryl-hydrazyl (DPPH)

Abstract

1,1-Diphenyl-2-Picryl-Hydrazyl (DPPH), a stable free radical, has been used for detecting antioxidant activity in chemical analysis. However, it is still unknown if DPPH triggers free radical injury in cardiac tissue. In order to establish a simple free radical-injured isolated heart model, we investigated the action of DPPH on isolated guinea pig heart by Langendorff perfusion and compared it with cardiac effect of superoxide anion (O 2 ·−), generated by the hypoxanthine (HX)–xanthine oxidase (XO) system. Free radical scavengers, dimethyl sulphoxide (DMSO), superoxide dismutase (SOD), and l-cysteine, were also used to analyze the characteristic of the DPPH free radical-derived cardiac dysfunction. In isolated guinea pig hearts, DPPH 100 nM and 250 nM in Krebs–Henseleit solution significantly decreased the left ventricular developed pressure (LVDP) and maximum velocity changes of left ventricular pressure (±LVdP/dt max), elevated the left ventricular end-diastolic pressure (LVEDP), and increased lactate dehydrogenase (LDH) release and thiobarbituric acid-reactive substances (TBARS) formation in cardiac tissue. The cardiac dysfunction induced by DPPH 250 nM was more intense than 100 nM. l-Cysteine improved the DPPH-impaired cardiac function, while DMSO and SOD had no beneficial effect on this injury. The cardiac membrane fluidity was decreased by DPPH. Free radical signals, detected by electron spin resonance (ESR) in the DPPH-injured heart, were reduced by l-cysteine-treatment. These results suggest that DPPH free radical-induced cardiac dysfunction is attributed to neither the superoxide anion nor the hydroxyl radical. In conclusion, our data indicate that DPPH-induced isolated heart dysfunction serves as a simple and reproducible free radical-injured heart model.