Vol. 275, Issue 4, H1225-H1235, October 1998
Are interatrial band myocytes maximally hypertrophied in
normal canine hearts?
Paul C.
Dolber,
Robert P.
Bauman,
Judith C.
Rembert, and
Joseph
C.
Greenfield Jr.
Department of Surgery and Division of Cardiology, Department of
Medicine, and Department of Pathology, Duke University Medical
Center, Durham 27710; and Cardiology Section, Medical Service and
Research and Development Service, Veterans Affairs Medical Center,
Durham, North Carolina 27705
In canine right atrial hypertrophy, the
cross-sectional area
(Axs) of right
atrial myocytes increases, whereas the
Axs of the
broader interatrial band myocytes does not. In the current study,
myocyte reconstructions showed that right atrial myocyte length
increased in proportion to
Axs in right
atrial hypertrophy. On the other hand, mean interatrial band myocyte
length in both normal and right atrial hypertrophy dogs was roughly
inversely proportional to mean
Axs, as expected
if interatrial band myocyte volume was constant. Plotting mean
Axs vs. myocyte
length for individual interatrial band myocytes revealed a distribution
whose border defined a maximal volume curve; many myocytes were well beneath that curve. Mononuclear myocytes (generally diploid) were limited by a 65,000-µm3 curve,
which many binuclear myocytes (generally tetraploid) surpassed; myocyte
ploidy thus constrained myocyte volume. However, because many
mononuclear and binuclear myocytes had lower volumes, their failure to
hypertrophy cannot be attributed to attainment of the maximal volume
possible for their ploidy.
atrium; cardiac muscle; hypertrophy; myocyte size; ploidy
