Effect of cellular inhomogeneity on cardiac tissue mechanics based
on intracellular control mechanisms.
Landesberg, Amir, Vladimir S. Markhasin, Rafael Beyar, and Samuel
Sideman.
The Heart System Research Center, The Julius Silver Institute,
Department of Biomedical Engineering, Technion-Israel Institute of
Technology, Haifa, 32000 Israel, and Institute of Physiology, Urals
Branch of the Academy of Science, Russia
APStracts 2:0335H, 1995.
Our earlier description of the intracellular control (IC) of
contraction of a single cell, based on coupling calcium kinetics with
crossbridge cycling, is extended here to study the performance of a
multicellular inhomogeneous tissue common in pathophysiological
situations. Inhomogeneity in calcium affinity or in crossbridge
kinetics is first simulated by analyzing two fiber segments connected
as parallel or serial duplexes. The calculated characteristics of the
parallel duplex are tested against our experimental data with two
parallel nonuniform rat papillary fibers. The predicted serial duplex
behavior is compared with reported experimental data of the effects
of segmental hypoxia along a papillary fiber. Fiber inhomogeneity
leads to polyphasic contraction of the fiber segments, reduces muscle
length shortening, and affects the control of relaxation. Next, we
investigate the force generated by a nonuniform tissue containing
small areas of necrosis, evident in subendocardial infarction. The
theoretical analysis suggests that the IC mechanism decreases the
extension of cell necrosis by lowering the energy consumption of the
viable cells in the ischemic zone. The study emphasizes the
importance of the IC in determining the global and local function of
the inhomogeneous myocardium.
Received 15 July 1994; accepted in final form 31 July 1995.
APS Manuscript Number H620-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.