Nonlinear dynamics of heart rate variability after superoxide dismutase inhibition in rats

Superoxide dismutase (SOD) is a crucial enzyme for endogenous oxidative balance. We tested how diethylthiocarbamate (DETC), a nonspecific SOD inhibitor and oxidant, influence heart rate variability (HRV). Fourteen Wistar rats (divided into two groups) with implanted subcutaneous ECG electrodes, maintained unrestrained in experimental setup. Time-series of 1024 RR intervals (RRi) were extracted from continuous ECG recording for HRV analysis. SOD activity was measured by dedicated assay kit. Intraperitoneal injection of DECT resulted in SOD inhibition by 30%. HRV analysis confirms a role of ROS in the regulation of sinoatrial rhythm. Increased HR after DETC injection was followed by a reduction in overall HRV including LF/HF. A significant reduction of the recurrence quantification analysis (RQA) parameters: %REC, %DET, DFAal and DFAa2 is indicative of some loss of complexity and self-similarity within the tested RRi time-series. The reduction of intrinsic harmonic correlations can be interpreted as a simplification of the regulatory feedback loops with more random heart rhythm poorly controlled by autonomic nervous system. Nonlinear dynamics methods such as RQA have a potential to increase the reliability of data in experimental studies.