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. 2014 May;16(5):584-90.
doi: 10.1093/ntr/ntt189. Epub 2013 Dec 3.

Brief Exposure to Secondhand Smoke Reversibly Impairs Endothelial Vasodilatory Function

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Brief Exposure to Secondhand Smoke Reversibly Impairs Endothelial Vasodilatory Function

Kranthi Pinnamaneni et al. Nicotine Tob Res. .
Free PMC article

Abstract

Introduction: We sought to determine the effects of brief exposures to low concentrations of tobacco secondhand smoke (SHS) on arterial flow-mediated dilation (FMD, a nitric oxide-dependent measure of vascular endothelial function), in a controlled animal model never before exposed to smoke. In humans, SHS exposure for 30 min impairs FMD. It is important to gain a better understanding of the acute effects of exposure to SHS at low concentrations and for brief periods of time.

Methods: We measured changes in FMD in rats exposed to a range of real-world levels of SHS for durations of 30 min, 10 min, 1 min, and 4 breaths (roughly 15 s).

Results: We observed a dose-response relationship between SHS particle concentration over 30 min and post-exposure impairment of FMD, which was linear through the range typically encountered in smoky restaurants and then saturated at higher concentrations. One min of exposure to SHS at moderate concentrations was sufficient to impair FMD.

Conclusions: Brief SHS exposure at real-world levels reversibly impairs FMD. Even 1 min of SHS exposure can cause reduction of endothelial function.

Figures

Figure 1.
Figure 1.
Experimental design for smoke exposures. The pre-smoke FMD measurement procedure consisted of baseline ultrasound measurement of artery diameter, occlusion of the artery for 5min (ischemia), release of occlusion, and a second ultrasound measurement of peak artery diameter. Diameter returned to baseline level within 5min. This pre-smoke FMD measurement was followed by exposure to smoke or clean air, and then the entire FMD measurement procedure (ultrasound, ischemia, release, ultrasound) was repeated to determine post-smoke FMD roughly 10min after the end of exposure. A smaller post-ischemia peak diameter indicated impaired FMD after SHS exposure. In most experiments, FMD was measured again to document recovery 30min later (i.e., 40min after the end of exposure).
Figure 2.
Figure 2.
Impairment of FMD, but not endothelium-independent vasodilation, after 30min of exposure to SHS. FMD was measured before and after 30min of exposure to SHS or clean air (n = 3/group). FMD was reduced after exposure to SHS, but not clean air. Nitroglycerin (NTG) administered immediately after post-exposure FMD measurement confirmed that endothelium-independent vasodilation was not impaired. Bars = SEM; *p < .0005 versus respective pre-exposure.
Figure 4.
Figure 4.
FMD is impaired by 1min of SHS exposure. RSP levels listed denote starting levels, which did not change appreciably during the 1min experiment. Four breaths is estimated at roughly 15 s. n = 8/group, *Significant impairment compared to average of pre-exposure and recovery.
Figure 3.
Figure 3.
Dose response of FMD impairment after varying SHS particle concentrations for 30min. Exact values are shown in Supplementary Figure S3 online. (A) Baseline FMD, before exposure to SHS at concentrations starting at 0, 67, 180, 670, and 6,000 µg/m3. Dots represent individual rats; n = 8/group except for n = 7 for 6,000 µg/m3. Dashed line connects mean FMD values at each subsequent SHS exposure level. (B) FMD measured ~10min following 30-min SHS exposure. Solid line is fit using the two-component spline at mean post-exposure FMD levels for each group and dashed line shows mean baseline levels (from panel A). The relationship between SHS concentration and FMD impairment is dose-dependent up to the 670 µg/m3 peak exposure, then the effect appears to saturate (that is, the slope higher than 670 µg/m3 is not significantly different from 0). The seven data points for the “6000” group overlap and are not all distinguishable. (C) Thirty minutes later, FMD has recovered to baseline. In the 670 µg/m3 starting group only, recovery FMD has slightly surpassed the baseline value but this difference was not significant. Solid line is fit using the two-component spline at mean recovery FMD levels for each group and dashed line is mean baseline levels (from panel A).

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