Papillary muscles split in the presence of 2,3-butanedione monoxime
have normal energetic and mechanical properties.
Kiriazis, Helen, and Colin L. Gibbs.
Department of Physiology, Monash University Clayton, Victoria 3168,
AUSTRALIA
APStracts 2:0241H, 1995.
A number of studies have used 2,3-butanedione monoxime (BDM) to avoid
myocardial damage when cutting small muscle preparations from large
hearts. The present study investigates the mechanical and energetic
effects of varying muscle cross-sectional area (CSA) by dissection in
physiological saline containing BDM. Using adult rat hearts three
muscle groups were obtained: whole left ventricular papillary muscles
(WHOLE) and left ventricular papillary muscles split longitudinally
in the presence of 30 mM BDM, removing around 10% (BDMSP1) or 40-50%
(BDMSP2) of the muscle (5 animals in each group). The isolated muscle
preparations were studied at 27 degrees C and stimulated at 1/6 Hz.
The WHOLE and BDMSP1 preparations had comparable CSAs; in
isotonically contracting muscles working against a range of
afterloads, work, enthalpy (energy use) and mechanical efficiency
(work/enthalpy x 100%) were similar for these two groups. In
addition, isometric performance (eg., developed stress (force/CSA),
length-tension relation, contraction time-course) were also similar
for these two groups. The thinner BDMSP2 preparations showed an
enhanced mechanical performance in comparison to the WHOLE and BDMSP1
groups. This outcome was in accordance with literature data
documenting a negative correlation between stress and CSA. The
results suggest that BDM-split and intact papillary muscles of
similar CSA have comparable energetic and mechanical properties.
Received 19 October 1994; accepted in final form 1 June 1995.
APS Manuscript Number H936-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.