Abstract
BACKGROUND: Heart rate variability (HRV) as a marker reflects the activity of the autonomic nervous system. The prognostic significance of HRV for cardiovascular disease has been reported in clinical and epidemiological studies. Our laboratory has reported alterations in rat heart rate variability (HRV) due to increasing activity of both sympathetic and parasympathetic nervous system after pulmonary exposure to multi-walled carbon nanotubes (MWCNTs). This suggests that pulmonary inhalation of engineered nanoparticles (ENs) may lead to functional changes in the cardiovascular system. The present study further investigated the effects of inhaled MWCNTs on the cardiovascular system and evaluated the correlation between the alterations in HRV and changes in cardiovascular function. METHODS: Male Sprague-Dawley rats were pre-implanted with a telemetry device and exposed by inhalation to MWCNTs for 5 h at a concentration of 5 mg/m(3). The electrocardiogram (EKG) and blood pressure were recorded in real time by the telemetry system at pre-exposure, during exposure, and 1 and 7 days post-exposure. In vivo cardiac functional performance in response to dobutamine was determined by a computerized pressure-volume loop system. RESULTS: Inhalation of MWCNTs significantly increased both systolic and diastolic blood pressure and decreased heart rate in awake freely moving rat. Additionally, inhalation of MWCNTs also reduced cardiac stroke work, stroke volume, and output in response to dobutamine in anesthetized rats. CONCLUSIONS: Inhalation of MWCNTs altered cardiovascular performance, which was associated with MWCNT exposure-induced alterations in the sympathetic and parasympathetic nervous system. These findings suggest the need to further investigate the cardiovascular effects of inhaled MWCNTs.