[Submicroscopic changes in the luminal cells of the endometrium in cows during the estrus cycle].

The structure of luminal epithelium cells in the endometrium of a cow shows little variation during the sexual cycle. Various coarse and irregular microvilli are produced on the surface of cells in pro-oestrus and oestrus. Starting from pro-oestrus, the relative volume of mitochondria increases to culminate in met-oestrus and di-oestrus. Their highest number was observed in oestrus; in met-oestrus they enlarge and many of them gradually disintegrate during di-oestrus. The maximum development of granular endoplasmic reticulum was observed in oestrus. The quantitative proportion of smooth membranes is small and their volume and surface area increase from the lowest values in di-oestrus up to culmination in oestrus. The highest number of lysosomes was observed at the end of sexual cycle and in pro-oestrus. In oestrus and met-oestrus the apical parts of cytoplasm contain many smooth-walled vesicles and cisterns.