AJP - Heart and Circulatory Physiology, Vol 242, Issue 1 68-H78, Copyright © 1982 by American Physiological Society
Direct measurement of sarcomere length from isolated cardiac cells
K. P. Roos, A. J. Brady and S. T. Tan
Isolated cardiac muscle cells enzymatically digested with collagenase and
hyaluronidase from whole rat myocardium demonstrate the characteristics of
an intact membrane in that they tolerate millimolar concentrations of free
Ca2+ and exhibit phasic contractions with electrical excitation. These
isolated cells maintain their characteristic A-I band striation patterns
when at rest or during contraction. An apparatus has been developed to
directly image these cells with phase-contrast micrography onto a
1,728-element charge-coupled device photodiode array for rapid data storage
in a digital computer. The digitized striation pattern profile was analyzed
for individual and average sarcomere spacing. In isotonic media the average
resting sarcomere length ranged from 1.77 to 1.91 micrometers in 13 cells,
with a mean length of 1.83 +/- 0.12 micrometers. Electrically stimulated
phasic contractions in three cells demonstrated a synchronous 20% decrease
in sarcomere spacing to a mean of 1.51 micrometers. Striation spacing
decreased under hypertonic stress but elongated only up to 1.93 micrometers
in hypotonic solutions, suggesting that some internal elastic constraint
exists that limits elongation of the cell.
