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differences noted based on filter, design, tar, nicotine or CO yield. This research was done in
the 1980s and the relationship to what is made and sold now here in New Zealand has not
been studied. Many studies have demonstrated that both peak and plateau NO is lower in
smokers than non-smokers who are otherwise 'healthy' with normal lung function (Persson,
Zetterstrom et al. 1994; Schilling, Holzer et al. 1994; Kharitonov, Robbins et al. 1995;
Robbins, Millatmal et al. 1997; Verleden, Dupont et al. 1999; Balint, Donnelly et al. 2001;
Mazzone, Cusa et al. 2001; Hogman, Holmkvist et ^1.200.2; Horvath, Donnelly et al.2O04).
In mild asthmatics, smokers also had a lower level of exhaled NO when compared to non-
smokers (Persson, Zetterstrom et al. 1994; Verleden, Dupont et al. 1999; Horvath, Donnelly et
al. 2ffi4; McSharry, McKay et al. 2005). Nasal NO measurements in 'healthy' normal and
asthmatic smokers compared with their non-smoking counterparts were also reduced
(Robbins, Millatmal et al. 1997; Olin, Hellgren et al. 1998). This reduction of NO was
correlated with 'pack years' in current (McSharry, McKay et al. 2005) and ex-smokers
(Corradi, Majori et al. 1999). Two studies also found significant reductions in levels of
exhaled NO and NO output in a total of ll8 healthy infants exposed to pre-natal cigarette
smoke compared to the non-exposed (Hall, Reinmann et al.2OO2; Frey, Kuehni et al. 2OO4).
The effects of a single cigarette have also been studied. A transient reduction in peak exhaled
NO occurs immediately (Kharitonov, Robbins et al. 1995) and at 50 minutes with a co-
incident rise in HzOz (Horvath, Donnelly et al. 2OO4). However another study found an
increase level of NO at one and ten minutes (Chambers, Tunnicliffe et al. 1998) while a fourth
found no change in the levels of exhaled NO, S-nitrosothiol or nitrotyrosine at 30 and 90
minutes, although nitrite and nitrate levels were significantly increased (Balint, Donnelly et al.
2001). A decrease in plasma nitrate and nitrite concentrations were seen after smoking a
single 'real' cigarette compared to a sham cigarette (Tsuchiya, Asada et al.2002). Passive
exposure and active smoking in usual non-smokers resulted in a reduction in the level of
exhaled NO when measured every 15 minutes to one hour (Yates, Breen et al. 2001).
Recently a murine model showed that cigarette smoke caused a reduction of NO by
decreasing iNOS mRNA transcription but did not alter the iNOS mRNA half life once already
developed (Hoyt, Robbins et al.20O3). It may be that the NO in the cigarettes operates as a
negative feedback mechanism, resulting in reduction of activity of the NOS enzymes.
The effect of quitting smoking on the subsequent levels of NO has also been examined. In 20
smokers, nine that were able to refrain from smoking for four weeks resulted in increased
levels of exhaled NO, which was no longer significantly lower than controls (Hogman,
Holmkvist et al.20O2). Fourteen smokers had an increase in their exhaled NO compared to
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