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The Journal of Thoracic and Cardiovascular Surgery, Vol 103, 936-944, Copyright © 1992 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
P Menasche, C Grousset, Y Gauduel, C Mouas and A Piwnica
The reduced thiol pool of myocardial tissue represents an important defense
mechanism against oxygen toxicity. Since the ischemia-induced depletion of
this pool might favor the cytotoxicity of oxygen-derived free radicals
produced during reperfusion, we assessed the effects of the thiol group
donor N-acetylcysteine in an isolated buffer-perfused rat heart model of
ischemia/reperfusion. Fifty hearts were studied. A first series of
experiments that consisted of two groups (n = 10) was designed to simulate
the conditions of standard cardioplegic arrest. Hearts were subjected to
180 minutes of cold (15 degrees to 18 degrees C) global ischemia and 1 hour
of reperfusion. The control group received crystalloid hyperkalemic
cardioplegic solution given every 30 minutes during arrest, and the treated
group received the same solution supplemented with N-acetylcysteine (0.04
mol/L). On the basis of comparisons of postreperfusion left ventricular
developed pressure, maximal dP/dt, and diastolic pressure,
N-acetylcysteine-containing cardioplegic solution afforded significantly
better protection. A second series of experiments was then undertaken to
assess the effects of N-acetylcysteine in hearts subjected to the sequence
of ischemic events that is inherent in transplantation procedures. Hearts
were cardioplegically arrested, stored for 5 hours at 2 degrees C,
subjected to 1 additional hour of ischemic arrest at 15 degrees to 18
degrees C, and reperfused for 60 minutes. Three groups (n = 10) were
studied that differed by the modalities of cardioplegic preservation used
during the poststorage ischemic interval. One group received multidose
unmodified cardioplegic solution. A second group received multidose
cardioplegic solution supplemented with N-acetylcysteine (0.04 mol/L), and
the third group was given only a single dose of N-acetylcysteine-enriched
(0.07 mol/L) cardioplegic reperfusate at the end of arrest. Multidose N-
acetylcysteine-containing cardioplegic solution resulted in a significantly
better hemodynamic recovery than unmodified cardioplegic solution. The
protection afforded by N-acetylcysteine was lost when the drug was given
only at the time of reperfusion. We conclude that supplementation of
cardioplegic solution with N-acetylcysteine markedly improves postarrest
recovery of function, presumably through an enhancement of the reduced
thiol pool, which increases the capacity of reperfused myocardium to handle
the postischemic burst of free radical production. The clinical relevance
of these findings stems from the fact that thiol-containing drugs are
available for human use.
ARTICLES
Maintenance of the myocardial thiol pool by N-acetylcysteine. An effective means of improving cardioplegic protection
Department of Cardiovascular Surgery, Hopital Lariboisiere, Paris, France.
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