[Histologic and histochemical study of placentomes in cows after induced labor]

The placentomes were extirpated from 16 cows after parturition induced with 750 micrograms cloprostenol or 20 mg dexamethasone on the 277th day of gravidity, on an average, from 9 cows after spontaneous parturition, and from 7 cows after hysterectomy in the eighth month of gravidity. In the cows with induced calving the foetal placenta was not expelled within 12 hours after calving in 68.7% of the cases whereas in the spontaneous parturitions this proportion was only 22.2% of cases. The placentomes obtained immediately after calf expulsion, and then after four and eight hours, were subjected to histological and histochemical examination. In the terminal crypts of the placentome in cross sections obtained from cows which expelled the placenta in time after natural and induced parturitions, the number of binuclear cells of the fetal syncytium and of cells of the dam epithelium (P less than 0.001) was found to be significantly lower than in the cases of afterbirth retention (1.2 and 3.9; 6.4 and 18.5). The cells of the cow's epithelium of the expelled placentae had a higher activity of acid phosphatase and lipids and the foetal syncytium had a higher activity of non-specific esterase. Increased alkaline phosphatase activity was characteristic of the cow's epithelium in the cases of subsequent retention of afterbirth. These findings should be taken into account in efforts for developing new methods of the induction of parturition if the undesired occurrence of afterbirth retention is to be reduced.