Effect of Additions of Sodium and Potassium and of Peritoneal Dialysis with a Hypotonic Solution of Sodium Chloride on the Sodium and Potassium Contents of the Maternal and Fœtal Serum and the Amniotic Fluid of Rats

Abstract

ELECTROLYTIC changes undergone by the mother will lead, both in man and animals, to similar changes in the fœtus within a few hours^1,2. We have been able to establish that when gravid rats and guinea pigs are subjected to a 2–3-day period of thirsting there is serious damage of the fœtus at the end of pregnancy—a large number of stillbirths or of non-viable young³. In order to study the effects of short-term additions, Wistar rats, weighing about 200 gm., were given, on the nineteenth day of pregnancy, 1.7 m.equiv./100 gm. body-weight of sodium in a 20 per cent sodium chloride solution, or 0.8–l.5 m.equiv./100 gm. body-weight of sodium was removed by peritoneal dialysis with 0.5 per cent sodium chloride solution. Another series of animals was given 1.5 m.equiv. potassium in isotonic solution of potassium chloride, intraperitoneally. As there was rapid renal elimination of potassium, 1.0 m.equiv. potassium was administered intraperitoneally to a further series of animals after bilateral nephrectomy. At fixed periods samples of blood from the vena cava inf., of amniotic fluid and of fœtal blood from the umbilical vessels were taken from the animals, which had been anæsthetized with ether, and the sodium and potassium in the serum and amniotic fluid were determined by photometric flashes. We used lithium as a standard and utilized the emission-increasing effect of methanol⁴ when determining the potassium content. The animals were given neither food nor drink during this time.