From the Division of Cardiology, Kumamoto University School of Medicine,
Kumamoto, Japan.
Correspondence to Kiyotaka Kugiyama, MD, Division of Cardiology, Kumamoto University School of Medicine, Honjo 1–1-1, Kumamoto City, Japan 860-8556. E-mail kiyo{at}gpo.kumamoto-u.ac.jp
Abstract
Background—Oxygen free radicals have
been shown to cause endothelial vasomotor dysfunction.
This study examined the effect of reduced glutathione (GSH), an
antioxidant, on human coronary circulation.
Methods and Results—Responses of epicardial diameter and blood
flow of the left anterior descending coronary artery to
intracoronary infusion of acetylcholine (ACh, 50 µg/min) were
measured by quantitative coronary angiography and Doppler
flow-wire technique, respectively, before and during combined
intracoronary infusion of GSH (50 mg/min) or saline in 26
subjects with no significant coronary stenosis. GSH
infusion suppressed the constrictor response of epicardial diameter to
ACh and enhanced the increase in blood flow response to ACh.
Furthermore, GSH potentiated the coronary dilator effect of
nitroglycerin. A beneficial effect of GSH on the
epicardial diameter response to ACh was observed in a subgroup of
subjects with
Conclusions—The results indicate that GSH improved
coronary endothelial vasomotor function,
particularly in subjects with coronary risk factors, and it
potentiated the vasodilator effect of nitroglycerin in
human coronary arteries.
Intracellular reduced
glutathione (GSH) has an important role in protection of
endothelial cells from oxygen free radicals, leading to
prevention against endothelial dysfunction in arteries
exposed to oxidative stress.1 2 Although
extracellular GSH is not effectively transported into cells, exogenous
addition of GSH is shown to cause a substantial increase in
intracellular GSH concentration and a severalfold increase in
concentration of intracellular and extracellular cysteine, a potent
antioxidant, in cultured endothelial cells and in
humans.3 4 5 Both GSH and cysteine can react with
NO to form S-nitrosothiols, which stabilize NO derived from
endothelium and organic nitrates and increase the
vasodilator action of NO.6 7 The present
study was thus conducted to assess the effect of intracoronary
infusion of GSH on vasomotor reactivity in human coronary
arteries.
Methods
Study Subjects
Study Protocol
Quantitative Coronary Angiography and Measurement of
Coronary Blood Flow
Statistical Analysis
Results
Response to GSH and Saline Alone and in Combination With
ACh
We also examined whether the presence of coronary risk factors
altered the effect of GSH on the epicardial arterial
diameter response to ACh. A beneficial effect of GSH on epicardial
diameter response to ACh was observed in a subgroup of 7 subjects with
Response to Nitroglycerin
Discussion
This is the first study to show that intracoronary
infusion of GSH suppresses constriction of epicardial
arterial diameter and/or converts constriction to dilation
in response to ACh in human coronary arteries. Furthermore, GSH
enhances the increase in coronary blood flow response to ACh.
The effects of GSH may be explained by at least 3 possible mechanisms:
(1) improvement of redox state in endothelium, leading
to restoration of endothelial functions, including NO
synthase1 2 ; (2) formation of nitrosothiols with
endothelium-derived NO and prevention of NO
inactivation by oxygen free radicals6 ; and (3)
augmentation of guanylate cyclase activation in smooth
muscle.7
It has been shown10 11 that oxygen free radicals
cause an imbalance in intracellular redox state in
endothelial cells and inactivate
endothelium-derived NO, leading to
endothelial dysfunction and impairment of
endothelium-dependent vasorelaxation in arteries of
patients with coronary risk factors and in atherosclerotic
arteries. In fact, the present study demonstrated that
endothelium-dependent dilation of epicardial
coronary arteries in response to ACh was impaired in subjects
with risk factors compared with those without risk factors. The
present study showed that the beneficial effect of GSH on the
response of epicardial diameter to ACh was observed in subjects with
risk factors but not in those without risk factors. Furthermore, the
present study showed that GSH potentiated the coronary
dilator response to nitroglycerin. However, GSH-induced
potentiation of the dilator action of nitroglycerin,
which shares a final common pathway through guanylate
cyclase activation with endothelium-derived NO, was
comparable between subjects with and without risk factors. Taken
together, effects of GSH on the pathway of ACh-induced vasorelaxation,
prior to guanylate cyclase activation in smooth muscle may
be involved in mechanisms of GSH-induced improvement of the epicardial
vasomotor response to ACh in subjects with risk factors. Thus, it is
suggested that GSH improved endothelium-dependent
dilation in response to ACh in part through restoration of
intracellular redox imbalance and prevention of NO inactivation in
endothelium. GSH administration may be useful in
patients with coronary artery disease, both as a result of
improvement of endothelial dysfunction and augmentation
of nitroglycerin-induced vasodilation and
antiplatelet activity.
In conclusion, intracoronary infusion of GSH improved the
endothelial vasomotor response to ACh, particularly in
subjects with coronary risk factors, and it potentiated the
vasodilator effect of nitroglycerin in human
coronary arteries.
Received January 27, 1998;
revision received April 16, 1998;
accepted April 17, 1998.
References
© 1998 American Heart Association, Inc.
Brief Rapid Communication
Intracoronary Infusion of Reduced Glutathione Improves Endothelial Vasomotor Response to Acetylcholine in Human Coronary Circulation
1 coronary risk factors but not in a subgroup
without risk factors. Saline infusion did not have any effects.
Key Words: antioxidants • free radicals • endothelium-derived factors • acetylcholine
This study comprised 26 consecutive subjects (mean age, 62
years; range, 46 to 72 years; 14 men and 12 women) who underwent
diagnostic cardiac catheterization for
evaluation of atypical chest pain. All of the study subjects had
angiographically normal coronary arteries (<10%
stenosis) and no coronary spasm during
intracoronary infusion of acetylcholine
(ACh).8 9 All medications were withdrawn 3 days
before study. None of the study subjects had taken pharmacological
doses of antioxidants for at least 1 month before the study. No subject
had previous myocardial infarction, congestive heart failure,
cardiomyopathy, valvular heart disease, or
other serious diseases. Written informed consent was obtained from all
subjects before study. The study was conducted in agreement with the
guidelines approved by the ethics committee at our institution.
ACh (50 µg/min) was infused directly into the left
coronary artery through a Judkins catheter for 1 minute.
Fifteen minutes after ACh infusion, GSH (50 mg/min at a rate of 2
mL/min for 6 minutes; Yamanouchi Co) was infused into the left
coronary artery through a Judkins catheter in 14 subjects (GSH
group), and saline (0.9%) as a placebo for GSH was infused in the
remaining 12 subjects (saline group) in an otherwise identical manner
as GSH. This dose of GSH yielded 1.2±0.1 mmol/L of GSH plasma
concentration in coronary sinus, concentrations that were
reported to increase intracellular GSH level by 
2-fold in cultured
endothelial cells.4 During the
last minute of GSH or saline infusion, ACh (50 µg/min) was
simultaneously infused into the left coronary
arteries in the same manner as before the infusion of GSH or saline.
After an additional 10 minutes, nitroglycerin (250
µg) was intravenously injected, and coronary
angiography was performed in multiple projections. Coronary
angiography and measurements of coronary blood flow and
hemodynamics were performed before and at the end of
each infusion. All drugs were dissolved in 0.9% saline in a sterile
manner and kept at 37°C. Risk factors, age, and sex were matched
between GSH (62±4 years old, 8 men and 6 women) and saline (61±3
years old, 6 men and 6 women) groups. Seven subjects in the GSH group
and 6 in the saline group had 1 coronary risk factor, defined
as history of current smoking,
hypercholesterolemia (>240 mg/dL),
hypertension (>140/90 mm Hg or antihypertensive medication), and
diabetes mellitus.
A quantitative coronary angiographic study was performed
in the same manner as described in previous
reports.8 9 In brief, the trunk of the left
anterior descending coronary artery (LAD) was divided into
proximal and distal segments of equal length. The luminal diameter at
the center of each segment was measured quantitatively with the use of
a computer-assisted coronary angiographic analysis
system (Cardio 500, Kontron Instruments) by 2 observers blinded to the
study protocol. Blood flow velocity was measured in 6 subjects in the
GSH group and 10 in the saline group by use of a 0.014-in wire equipped
with a Doppler crystal at its tip (Flow Wire, Cardiometrics) that
was advanced through the Judkins catheter and carefully positioned in a
straight proximal segment of the LAD.9
Coronary blood flow was calculated from blood flow velocity and
arterial diameter.9 Responses of
coronary artery diameter and blood flow to infusions of ACh,
GSH, and saline were expressed as percentage changes from baseline
coronary diameter and blood flow measured just before each
infusion, respectively.
Data are expressed as mean±SEM unless otherwise indicated.
Differences between 2 means were compared by paired or unpaired
Student's t test. For comparison of coronary
luminal diameters in subgroups with and without risk factors, 2-way
ANOVA for repeated measures, followed by Bonferroni's multiple
comparison test, was used. A value of P<0.05 was considered
statistically significant.
Infusion of GSH alone did not significantly change epicardial
coronary diameters or blood flow. However, the combined
infusion of GSH and ACh suppressed the constrictor response of
epicardial coronary diameter to ACh (percentage change of
distal diameter from baseline [minus sign denotes constriction],
-7.7±2.9% before GSH versus -0.9±2.1% during GSH;
P<0.01; Figure 1
).
Furthermore, GSH enhanced the increase in coronary flow
response to ACh (percentage increase from baseline, 98±16% before GSH
versus 140±20% during GSH; n=6; P<0.05). GSH did not
significantly affect heart rate or mean blood pressure. Saline infusion
alone or in combination with ACh did not have any effect (percentage
change of distal diameter from baseline in response to ACh,
-8.2±2.2% before saline versus -9.6±2.8% during saline,
P=NS; percentage increase in blood flow from baseline in
response to ACh, 92±14% before saline versus 98±12% during saline,
P=NS). Coronary diameter and flow at baseline and
their responses to ACh alone were each comparable between subjects
treated with GSH and those given saline.
View larger version (27K):
[in a new window]
Figure 1. Percent changes in lumen diameter from baseline in
response to acetylcholine (ACh) alone and in combination with
glutathione (GSH) in proximal and distal segments of epicardial
coronary arteries. 
, Subjects with coronary risk
factors; 
, subjects without risk factors. Mean±SEM was calculated
from subjects with and without risk factors.1 coronary risk factor (smoking,
hypercholesterolemia, hypertension, or diabetes
mellitus), whereas it was not observed in a subgroup of the remaining 7
subjects without risk factors, as shown in Figure 2. Age and sex were matched between the
subgroups with and without risk factors. The subgroup with risk factors
showed significantly greater constriction of epicardial
coronary arteries in response to ACh alone than the subgroup
without risk factors (Figures 1
and 2).
View larger version (22K):
[in a new window]
Figure 2. Effect of presence of coronary risk
factors on percent changes in coronary lumen diameter from
baseline in response to acetylcholine (ACh) alone and in combination
with glutathione (GSH) in proximal and distal segments of epicardial
coronary arteries. Open bars, ACh alone; solid bars, combined
infusion of ACh and GSH.
The dilator response of epicardial diameter to
nitroglycerin was significantly greater in subjects
treated with GSH than in subjects treated with saline (percentage
increase in proximal diameter from baseline, 28±3% in the GSH group
versus 19±2% in the saline group; P=0.02). The
coronary dilator effect of nitroglycerin in
both the GSH and saline groups was comparable between subgroups of
subjects with and without risk factors (percentage increase in proximal
diameter from baseline, 26±3% in the GSH group with risk factors
versus 28±3% in the GSH group without risk factors, P=NS;
18±2% in the saline group with risk factors versus 19±2% in the
saline group without risk factors, P=NS).
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