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(Circulation. 1999;99:2565-2570.)
© 1999 American Heart Association, Inc.
Clinical Investigation and Reports |
From Cardiothoracic Surgery (V.J.O., P.B.J.B., J.R.P., P.J.R.B., M.H.Y.) and Cardiac Medicine (S.E.H.), National Heart and Lung Institute at Imperial College School of Medicine, London, UK; Nephrology Laboratory (M.C.M.), Klinikum Essen, Essen, Germany; and Klinik III fur Innere Medizin (O.Z., M.B.), Universitat zu Köln, Germany.
BackgroundPotential cardiac
donors show various degrees of myocardial dysfunction, and the most
severely affected hearts are unsuitable for transplantation. The cause
of this acute heart failure is poorly understood. We investigated
whether alterations in calcium-handling proteins, ß-adrenoceptor
density, or the inhibitory G protein Gi
could account for this phenomenon in unused donor hearts (n=4 to 8). We
compared these with end-stage failing hearts (n=14 to 16) and
nonfailing hearts (n=3 to 12).
Methods and ResultsMyocardial samples were obtained from
unused donor hearts displaying ejection fractions <30%. Both
trabeculae and isolated myocytes responded as poorly as
those from the group of failing hearts to increasing stimulation
frequency with regard to inotropic function in vitro. Immunodetectable
abundance of sarcoplasmic reticulum calcium-ATPase and sodium calcium
exchanger were greater (177%; P<0.01) and smaller
(29%; P<0.01), respectively, in the unused donor
hearts relative to the failing group, which suggests that alterations
of these proteins are not a common cause of contractile dysfunction in
the 2 groups. Myocytes from the unused donor group were desensitized to
isoprenaline to a similar degree as those from the failing heart group.
However, ß-adrenoceptor density was reduced in the failing
(P<0.001) but not in the unused donor heart group
(P=0.37) relative to the nonfailing heart group (n=5).
Gi
activity was increased in samples from unused donor
and failing hearts relative to nonfailing hearts
(P<0.05).
ConclusionsIncreased activity of the inhibitory G
protein Gi
is a significant contributory factor for
impaired contractility in these acutely failing donor
hearts.
Key Words: transplantation heart failure proteins receptors, adrenergic, beta contractility
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