AJP - Heart and Circulatory Physiology, Vol 253, Issue 2 432-H443, Copyright © 1987 by American Physiological Society
Tunneling cell processes in myocytes of stretched mouse atria
E. Page, G. E. Goings, B. Power and J. Upshaw-Earley
Serial section electron micrographs of mouse atria stretched in vitro show
that myocytes have cell processes which tunnel into adjacent myocytes for 8
microns or more. The tunneling cell processes (TCP) (diam 4-6.2 microns)
lack myofibrils and organelles associated with atrial peptide secretion.
The glycogen-rich TCP cytoplasmic matrix contains conspicuous tubules and
vesicles originating from endoplasmic reticulum and resembling free
sarcoplasmic reticulum (SR). TCP are surrounded by a plasmalemma derived
from their myocyte of origin, the plasmalemma of the tunneled myocyte, and
an intervening narrow compartment continuous with the interstitial space.
Profiles having the characteristics cytoplasmic structure of TCP are also
found both in the interstitial space between myocytes and near the
longitudinal terminations where myocyte ends about on the interstitial
space. We suggest that TCP tubules and vesicles may proliferate and/or
transport in response to stretch, might be free SR, and may respond to
stretch-activated changes in ionic composition or potential of the
surrounding myocyte and narrow intercellular compartment.
