Surface features of exfoliated vaginal epithelial cells during the oestrous cycle of the rat examined by scanning electron microscopy.

The purpose of this study was to document vaginal exfoliative cytology (smears) as seen with the scanning electron microscope during the first, hormonally induced oestrous cycle of PMS-LH treated immature rats and to compare it with the surface morphology of the intact vaginal wall of similarly treated rats. Exfoliated cells were obtained by vaginal lavage 7--9 hours (pro-oestrus), 18--20 hours (oestrus), 28--34 hours (metoestrus) and 60--64 hours (dioestrus) after administration of luteinizing hormone. Cell suspensions were plated upon moistened Millipore filters according to the method of Shelton & Orenstein (1975). The pro-oestrous stage was characterized by round to ovoid cells with numerous short microvillus-like protrusions and blebs. The vaginal wall exhibited folds lined by cells with many short microvilli. Oestrus was characterized by flattened angular cells with either blebs, microridges or both. The intact wall exhibited 'flattened mosaics' of cells, some in the process of desquamation, with ridges and pits. Metoestrus resembled oestrus, except for the presence of a few leucocytes in the plated specimens. Dioestrus was characterized by an abundance of pleomorphic leucocytes with blebs of varying sizes. The vaginal wall appeared as a 'cobblestone' pavement with cells of varying sizes and shapes possessing numerous short, microvilli with bulbous endings.