Concentration of oestrogens and histological changes in placentomes of cows at the ninth month of pregnancy and with retained membranes — Two experiments are described in the paper. In the first experiment, in 6 cows on 30, 15 and 5 days before parturition the levels of oestrone (El) and oestrone sulfate (E1S) were determined by the RIA and histological investigations of placentomes were performed. In the last month of pregnancy one could measure an increase in the level of oestrogens, especially El and morphological changes in the tissue of placentomes (loss of cryptal epithelium, migration of binucleate giant cells into the maternal placenta and decrease of their number). In the second experiment, in 6 cows with retained placenta and in 6 cows with physiological calving the level of El and E1S were determined during the last 7 days of gestation and the placentomes, obtained immediately after calving, were histologically examined. In the group of cows with retained placenta the concentration of El was lower and incomplete morphological changes of placentomes, like the presence of cryptal epithelium and a large number of binucleate giant cells were observed. The role of oestrogens in the process of placenta maturation before parturition is discussed.
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