AJP - Cell Physiology, Vol 235, Issue 5 168-C179, Copyright © 1978 by American Physiological Society
Possible role of gap junctions in activation of myometrium during parturition
R. E. Garfield, S. M. Sims, M. S. Kannan and E. E. Daniel
Gap junctions between smooth muscle cells of the myometrium of pregnant
rats were found only immediately prior to, during and immediately after
parturition by quantitative thin-section and freeze-fracture microscopy.
Ovariectomy of 16- to 17-days-pregnant rats resulted in premature
termination of pregnancy and the appearance of gap junctions. Methods that
prolonged normal pregnancy in rats or maintained pregnancy in
ovariectomized animals (progesterone treatment) prevented the appearance of
gap junctions. Gap junctions formed in tissues incubated for 24--96 h in
vitro without any hormonal influence. We propose that gap junctions are
essential for normal labor and delivery for synchronous contraction of the
muscle of the uterus. We present a model for control of parturition that
may apply to other animals including humans. The model proposes: 1) the
possible roles progesterone, prostaglandins, or estrogens may play in
initiating gap-junction formation; 2) that the formation of gap junctions
is a necessary step in activation of the myometrium leading to labor; and
3) that agents used to stimulate or inhibit labor may do so by affecting
gap junctions.
