Objective: The electrophysiologic properties of gap junctions between human myometrial smooth muscle cells were studied.
Study design: Double whole-cell patch clamp recordings were made on pairs of cells from primary cultures of myometrial cells from women undergoing cesarean section. Macroscopic gap junction currents were measured as the change in current in a cell held at a constant voltage while the other member of a pair was subjected to a test pulse of voltage. The blockade by halothane was examined.
Results: Mean junctional conductance between pairs of cells was 23 +/- 14 nanosiemens (n = 57). Instantaneous gap junction conductance was constant as a function of transjunctional voltage. For transjunctional voltages of < or = 50 mV, currents were constant during a 5-second test pulse. For larger voltages, however, the currents showed a time-dependent decay. The currents were blocked completely and reversibly with 3.5 mmol/L halothane. Single-channel conductances of 60 picosiemens and 15 picosiemens were observed.
Conclusion: This first study of gap junction currents in human myometrial cells confirms that connexin43 is the major functional constituent. Functional studies of myometrial gap junction channels may suggest new strategies for controlling uterine contractility.