| Interaction Effects of Ultrafine Carbon Black with Iron and Nickel on Heart Rate Variability in Spontaneously Hypertensive Rats Chuen-Chau Chang,1,2 Jing-Shiang Hwang,3 Chang-Chuan Chan,1 and Tsun-Jen Cheng 1Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, Taipei, Taiwan; 2Department of Anesthesiology, Taipei Medical University Hospital, Taipei, Taiwan; 3Institute of Statistical Science, Academia Sinica, Taipei, Taiwan Abstract
Background: Particulate matter (PM) has been reported to be associated with alterations in heart rate variability (HRV) ; however, the results are inconsistent. We propose that different components of PM cause the discrepancy. Objective: In this study, our goal was to determine whether different types of exposure would cause different HRV effects, and to verify the interactions between co-exposing components. Methods: Ultrafine carbon black (ufCB ; 14 nm ; 415 µg and 830 µg) , ferric sulfate [Fe2(SO4) 3 ; 105 µg and 210 µg], nickel sulfate (NiSO4 ; 263 µg and 526 µg) , and a combination of high-dose ufCB and low-dose Fe2(SO4) 3 or NiSO4 were intratracheally instilled into spontaneously hypertensive rats. Radiotelemetry data were collected in rats for 72 hr at baseline and for 72 hr the following week to determine the response to exposure. Effects of exposure on 5-min average of normal-to-normal intervals (ANN) , natural logarithm-transformed standard deviation of the normal-to-normal intervals (LnSDNN) , and root mean square of successive differences of adjacent normal-to-normal intervals (LnRMSSD) were analyzed using self-control experimental designs. Results: Both high- and low-dose ufCB decreased ANN marginally around hour 30, with concurrent increases of LnSDNN. LnRMSSD returned to baseline levels after small initial increases. We observed minor effects after low-dose Fe and Ni instillation, whereas biphasic changes were noted after high-dose instillations. Combined exposures of ufCB and either Fe or Ni resulted in HRV trends different from values estimated from individual-component effects. Conclusions: Components in PM may induce different cardioregulatory responses, and a single component may induce different responses during different phases. Concurrent exposure to ufCB and Fe or Ni might introduce interactions on cardioregulatory effects. Also, the effect of PM may be mediated through complex interaction between different components of PM. Key words: ambient particles, heart rate variability, interaction, iron, nickel, spontaneously hypertensive rats, ultrafine carbon black. Environ Health Perspect 115:1012–1017 (2007) . doi:10.1289/ehp.9821 available via http://dx.doi.org/ [Online 27 February 2007]
Address correspondence to T.J. Cheng, Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, 17 Xu-Zhou Rd., Rm 720, Taipei, Taiwan 10055. Telephone and Fax: +886-2-3322-8090. E-mail: tcheng@ntu.edu.tw We thank C.-W. Yeh for her technical assistance. We also thank the National Institute of Environmental Analysis, Taiwan Environmental Protection Administration (EPA) for their assistance on this project. This study was funded by the Taiwan EPA (grants NSC 94-EPA-Z-002-007 ; NSC 95-EPA-Z-002-011) and the National Science Council of Taiwan (grant NSC 94-2621-Z-002-019) . The authors declare they have no competing financial interests. Received 11 October 2006 ; accepted 27 February 2007.
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