Water and electrolyte composition of the bovine uterus in pregnancy

¹ Dairy Cattle Research Branch, Animal Husbandry Research Division, ARS, Agricultural Research Center, Beltsville, Maryland

Determinations of water, its extracellular-intracellular distribution and electrolytes were made in the uterus and placenta of the cow during pregnancy and parturition. The endometrium and fetal cotyledons showed a decrease in water content during the first half of pregnancy and relative constancy thereafter until term. Maternal cotyledons showed a steady decrease throughout gestation. The myometrial water content was slightly higher during the middle of pregnancy. Na and Cl values generally decreased during the first half of pregnancy. K content increased during gestation. Uterine water distribution during pregnancy was very similar to that observed during progesterone domination of the uterus, with 40–50% of the water in the extracellular phase. At parturition there was a sharp reversal to the distribution seen under estrogen influence, 60–70% being extracellular. The changes in water and electrolyte composition of the uterus during pregnancy are due mainly to the growth of the uterus and its contents and to the influence of hormonal factors.