Water, electrolyte, glycogen, and histamine content of rat uterus during pregnancy

¹ Dairy Cattle Research Branch, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland

Changes in uterine and placental constituents were studied during pregnancy in the rat. Amounts of H₂O, Na, Cl, K, glycogen, and histamine were determined at 3-day intervals throughout gestation. The most dramatic changes were observed in the concentrations of glycogen and histamine. Interdecidual tissue showed a fivefold increase in glycogen from day 9 to 21. Histamine decreased steadily in this tissue until at term there was less than half the initial value. Both fetal and maternal placenta contained more H₂O than interdecidual uterus, and electrolytes were lower. Maternal placental tissues showed marked H₂O depletion on day 15 but returned to former levels subsequently. The K level of the fetal placenta decreased sharply at term. Cl and Na in placental tissues were low at day 15. Glycogen in maternal placenta quadrupled during the last 8 days, whereas glycogen in fetal placenta diminished to one-third its earlier value. Histamine content of the fetal placenta increased during the last half of pregnancy.