Intraepithelial leucocytes in the bovine uterine tube

The epithelium of the uterine tube consists of ciliated cells and secretory cells. Basal cells are a third cell type observed in tubal epithelium and they are located principally in the basal part of the epithelium. The objectives of this study were to characterize these basal cells in normal and superovulated heifers and to determine whether they participate in the replacement of the ciliated and secretory cell populations. All heifers received cloprostenol (PG) to induce oestrus (day 0). Superovulated heifers received 24 mg pFSH at doses of 4.5, 3.5, 2.5 and 1.5 mg given twice daily. Control and superovulated heifers were slaughtered on days 1, 3, 5 and 7 of the oestrous cycle. Another group of normal cycling heifers was slaughtered on days 2-3 and 11-13 of the oestrous cycle and used for immunocytochemistry. Samples from ampulla, pre-isthmus and isthmus of the uterine tube were collected and processed for light and transmission electron microscopy. Quantitative examination by light microscopy showed that there was a significant difference in the number of basal cells between the regions of the heifers' uterine tube. On the basis of ultrastructure two populations of basal cells were observed. One (type I) had a nucleus with much condensed heterochromatin and very sparse cytoplasmic organelles. The second cell (type II) had a nucleus with heterochromatin typically clumped around the nuclear envelope. Its cytoplasm contained many organelles including a number of lysosomes. The ultrastructural features of these cells were similar in all regions and at all days of the oestrous cycle examined. Immunocytochemistry revealed that type I basal cells were lymphocytes and type II basal cells were macrophages.