Studies of connexin 43 and cell-to-cell coupling in cultured human uterine smooth muscle.

OBJECTIVE: The aim of this study was to assess the presence and the permeability of gap junctions between human uterine smooth-muscle cells in culture. STUDY
DESIGN: The uterine smooth muscles obtained from term-pregnant women were cultured. The presence of gap junction was evaluated by immunocytochemistry with gap junction protein antibodies and by measuring input resistance and intercellular spread of lucifer yellow. These measures also evaluated the permeability of gap junctions. Octanol, isoproterenol, dibutyryl cyclic adenosine monophosphate and forskolin were applied to the cultures to assess their effects on the permeability of gap junctions.
RESULTS: During culture, immunocytochemical staining of gap junction protein (connexin 43) was increased and input resistance was decreased on day 2 of culture versus day 21 (18.4 +/- 7.87 M omega day 2; 3.8 +/- 1.76 M omega, day 21; p < 0.001). However, the decrease in input resistance was related to cell density rather than time in culture (16.4 +/- 5.01 M omega, single cells on days 1 and 2; 5.3 +/- 2.35 M omega, high-density cultures on days 1 and 2; p < 0.001). Octanol increased input resistance and intercellular spread of lucifer yellow in confluent cultures; isoproterenol, dibutyryl cyclic adenosine monophosphate, and forskolin did not.
CONCLUSIONS: The increased staining of connexin 43 and the decreased input resistance during culture are evidence of elevated number of gap junctions between cells. The rapid and reversible increase in input resistance and decrease in spread of lucifer yellow by octanol are the result of decreased permeability of gap junctions. These two methods of modulation of gap junctions in human uterine smooth muscles are thought to be major mechanisms for the control of uterine contractility.