AJP - Heart and Circulatory Physiology, Vol 250, Issue 2 265-H275, Copyright © 1986 by American Physiological Society
Ultrastructure and function of isolated myocytes after calcium depletion and repletion
J. S. Frank, A. J. Brady, S. Farnsworth and G. Mottino
We describe a system in which the contractile response of a single isolated
Ca-tolerant rat myocyte can be monitored while stimulated in Ca-free (37
degrees C) and then Ca-containing medium. This same cell is then processed
for ultrastructural analysis. We find unattached isolated Ca-tolerant
myocytes can withstand Ca depletion and repletion. They respond to
stimulation after Ca repletion with healthy twitches and are structurally
intact. The cell surface of the isolated myocyte appears similar to that
seen in the intact myocytes even after 15 min in Ca-free solution. This is
in marked contrast to myocardial cells in tissue where Ca depletion causes
separation of the layers of the glycocalyx. When the cell is attached to a
fine pipette so that some of the sarcolemma is under stress, the sequence
of Ca depletion and repletion drives the cell into hypercontracture and
loss of structural integrity that is characteristic of the Ca paradox.
