CHANGES IN SECRETORY STATUS, CELL HEIGHT AND PERCENTAGE CILIATION OF EPITHELIAL LINING OF SHEEP FIMBRIA OVIDUCT DURING EARLY-PREGNANCY

Studies have shown that the biosynthetic activity of the fimbria ovidu ct in the sheep changes during the first few weeks of pregnancy. The o bjective of the present study was to determine whether the secretory e pithelial lining of the fimbria undergoes pregnancy-associated morphol ogical alterations in a concordant manner. Oviducts obtained from ovar iectomized, oestrous (day 0) and pregnant (day 1.5, 2, 3, 4, 6 and 16) ewes were analysed quantitatively and qualitatively using light and e lectron microscopy. The epithelium was low cuboidal in fimbria from ov ariectomized sheep, significantly increased in height at day 1.5 of pr egnancy, immediately decreased at day 2, and underwent an additional s light reduction at day 6 and day 16 of pregnancy. Ciliated and noncili ated cells were present in the epithelium at all reproductive stages. The proportions of ciliated and nonciliated cells varied during pregna ncy and ciliated cells were always the major cell type. Consistent wit h previous data, the secretory organelles of nonciliated epithelial ce lls obtained from ovariectomized ewes were poorly developed. Maturatio n of secretory organelles in nonciliated cells occurred at oestrus and was maintained until days 2-3 of pregnancy; regressive changes were t hen observed, characterized by atrophy of the Golgi apparatus and roug h endoplasmic reticulum, and increases in heterochromatin and pronounc ed nuclear folds. Large, electron-dense lipid droplets were present th roughout the cytoplasm of ciliated and nonciliated epithelial cells, b eginning at day 1.5 of pregnancy and increasing at later stages of pre gnancy. Apical protrusions and microvilli were observed at the luminal domains of nonciliated cells and were reduced in extent after day 3 o f pregnancy. Cells were extruded from the epithelial lining at day 16 of pregnancy. These data show that the epithelial lining of the fimbri a oviduct in the sheep undergoes distinct changes in cell height, perc entage ciliation and secretory organelle development during the first few weeks of pregnancy.