Sodium transport in the kidney and placenta in normal pregnancy and in experimental toxemia

Abstract

Under aerobic conditions, the steady state of sodium exchange has been measured with Na24 in slices of rat kidney cortex and placenta. In the steady state the total time of incubation was 60 minutes during which the O2 uptake was determined. At different time intervals samples of the medium and tissues were taken for measurement of Na by flame photometry and radioactivity. Tissues from nonpregnant and pregnant rats (14 to 20 days' gestation) fed a normal pellet diet were the controls. The results were compared with data obtained from pregnant and nonpregnant rats fed a vitamin E-deficient diet containing toxic fractions of oxidized cod liver oil. A steady increase of exchange up to the eighteenth day of gestation which then dropped to nonpregnant values was observed in kidney cortical tissue of normal pregnant rats. The renal tissue from animals on the toxemic diet showed a similar pattern, but they were slightly higher. In comparison, the Na of placental tissue from normal pregnant rats exchanged without variations during the whole gestation at about 100 per cent, and the placental tissue from rats on the special diet revealed wide distribution of the exchange rate curves. The QO2 indicated partial respiration dependency of the electrolyte transport variations only at the end of gestation. The results are compared with the rates of exchange of K, and the possible mechanisms by which the diet interferes with the exchange rates are discussed.