Lack of effect of ouabain on sodium transport across the rat placenta.

The umbilical vascular bed of the rat placenta was perfused in situ. Ouabain (10(-4)M) in the perfusion fluid had no effect on the unidirectional flux of Na+ from the maternal (electrically negative) to the foetal (electrically positive) side of the placenta, or on the transplacental potential difference. This was taken to indicate that there is no significant active transport of Na+ across the placenta of the rat.