© 1999 American Heart Association, Inc.
Original Contribution |
Analysis of the Presence and Physiological Relevance of Subconducting States of Connexin43-Derived Gap Junction Channels in Cultured Human Corporal Vascular Smooth Muscle Cells
From the Departments of Urology and Physiology & Biophysics (G.J.C.), Albert Einstein College of Medicine, Bronx, NY; Department of Physiology & Biophysics (P.R.B.), State University of New York at Stony Brook, Stony Brook, NY.
Correspondence to George J. Christ, PhD, Laboratory of Molecular & Integrative Urology, Room 744, Forchheimer Bldg, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461. E-mail christ{at}aecom.yu.edu
Abstract—Subconductance states
are a commonly observed feature of gap junction channels. Their overt
frequency and consistent appearance in both single and
multichannel records have led to speculation that they might be of
physiological importance in terms of altering the
rate of small solute transfer from cell to cell. Among the connexin
gene family, connexin43 (Cx43) is the most ubiquitous connexin that has
been shown to generate subconductive states. Therefore, it was the
explicit aim of this investigation to more fully evaluate the potential
contribution of human Cx43-derived subconducting states to
intercellular communication in cultured human corporal vascular smooth
muscle cells. To determine the weight of subconductive states in our
records, we analyzed amplitude histograms of multichannel
and single-channel data during the application of transjunctional
voltages larger than expected for physiological
conditions but still smaller than transjunctional voltages known to
induce lower conductive states (Vo>Vj). The
data clearly indicated that the subconducting states occupy only a
small fraction of the total channel open time. This was reflected by
the fact that the average open probability for the subconductive
state(s) determined from the 9 records analyzed was 
2%.
Closer inspection of the data revealed that the frequency of
subconductive states was actually higher than the frequency of the main
state conductance. In summary, recording conditions sufficient
for evaluation of the intrinsic gating characteristics of human
Cx43-derived gap junction channels have been used. Under these
conditions, our data clearly indicate that despite their greater
frequency, the duration of subconductance events is so short relative
to the main state duration as to render them physiologically
insignificant.
Key Words: connexin • vascular smooth muscle cell • gap junction
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