Abstract
Plasma osmolality and the levels of water, taurine, and total amino nitrogen (detected as ninhydrin-positive substances) have been measured in the cerebral cortices of nonpregnant and 19-day pregnant Wistar rats. Plasma osmolality fell by 11 mosmol/kg during pregnancy. Brain water content remained unaltered, but levels of taurine and ninhydrin-positive substances fell by 48.5 and 21.9%, respectively. It is suggested that one way in which brain cells are prevented from swelling during the mild hypoosmolality of pregnancy is through loss of cellular amino nitrogen, particularly taurine.