© 1999 American Heart Association, Inc.
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A Subpopulation of Cardiomyocytes Expressing 
-Skeletal Actin Is Identified by a Specific Polyclonal Antibody
From the Department of Pathology, University of Geneva-CMU, Geneva, Switzerland.
Correspondence to Prof Giulio Gabbiani, University of Geneva-CMU, Department of Pathology, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland. E-mail giulio.gabbiani{at}medecine.unige.ch
Abstract—The
NH2-terminal decapeptide of 
-skeletal actin that
contains a primary sequence specific for this isoform was used to raise
a polyclonal antibody in rabbits. Using sequential affinity
chromatography, we recovered from serum antibodies
reacting exclusively with -skeletal actin when tested by
immunoblotting and
immunofluorescence. Epitope mapping by means of
competition assays with synthetic peptides indicated that the acetyl
group and the first 9 amino acids are essential for specificity. The
monospecific antibody was then used to investigate the distribution of
-skeletal actin in the myocardium of newborn and normal
or hypertensive (with or without fibrotic areas) adult rats.
Immunostaining of normal heart revealed that
-skeletal actin is diffusely distributed within practically all
myocardial fibers of the newborn rat, whereas it is restricted to a
small proportion of adult rat cardiomyocytes, which appear
intensely stained. A correlation, albeit not complete, was found
between the distribution of -skeletal actin and ß-myosin heavy
chain. During cardiac hypertrophy induced by aortic
ligature between the renal arteries, the expressions of -skeletal
actin mRNA and protein were increased. The distribution of
immunostaining had a focal pattern similar to that of
normal adult rats, reactive fibers being more numerous and more
intensely stained compared with normal myocardium. Positive
fibers were particularly abundant at the periphery of fibrotic areas.
Using this antibody, we have demonstrated for the first time the
differential distribution of -skeletal actin in heart tissues.
Changes in the distribution of this isoform in hypertrophic heart
provide new insight into the mechanisms by which the heart adapts to
work overload. This antibody will prove useful in exploring the
mechanisms of expression of -skeletal actin and in defining its role
in physiological and pathological situations.
The full text of this article is available at
http://www.circresaha.org.
Key Words: actin isoform • cardiac hypertrophy • fibrosis • myocardium • hypertension
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