Oscillation of membrane potential in syncytiotrophoblast of human term placenta in culture.

The membrane potentials and resistances of the cultured syncytiotrophoblast of human chorionic villi obtained from normal term placentas were measured using a standard electrophysiological technique. The mean value of membrane potentials and resistances for 156 cells in the control tris-buffered saline at 37 degrees C were -40.0 +/- 1.2 mV and 8.6 +/- 0.7 M omega (mean +/- S.E.), respectively. The membrane potential was markedly affected by the change of external concentration of Ca++ or K+. In 32 cells among 156 cells examined, spontaneous oscillations of membrane potentials were observed. They oscillated between around -38 mV and -57 mV with the average frequency of 2.4 +/- 0.2 times per minute, accompanied by decrease in membrane resistance on each hyperpolarization. Although oscillations of membrane potentials have been observed in other cultured cells, this is the first report on the oscillation of membrane potential in the human trophoblast.