Human fetal membranes: investigations on membrane potentials and membrane 24Na permeability in vitro and the possible involvement of acetylcholine.

Amnion, chorion and amniochorion from human term placentae were mounted as a membranous partition in a suitable chamber. The existence of membrane potentials was investigated, but no evidence for their generation was seen either in control Earle's buffer or subsequent to the addition of 100 microM acetylcholine (ACh). Sodium movement was measured under isosmotic conditions by assessing the rate of radiosodium exchange down its radioactivity gradient. These measurements revealed that sodium exchange was independent of membrane orientation, occurred by diffusion and was unresponsive to the addition of ACh.