RESUMO
The short length of the rat estrous cycle makes them ideal for investigation of changes occurring during the reproductive cycle. The estrous cycle lasts for 4 days and is characterized as proestrus, estrus, metestrus and diestrus, The present study tried to modify a rapid cytological technique for analysis of the vaginal smear and compared it to the routine gynaecological stain [Papanicolaou, in an attempt to provide Fesearchers with a fast and practical way for the determination of the rat estrous cycle phases. Vaginal smears of 20 albino rats were collected. Half of the sin ears were stained by technique. A [using Methylene blue] while the other half was stained by technique B [Papamzicolaou stain]. The results were further verified by both light and scanning electron microscopic examination of the endometrium. The present study realized that staining of vaginal smear by the Papanicolaou stain [technique B] relatively took longer time, while Methylene blue stain [technique A] was less time consuming, and could be easily applied in daily settings; requiring only slides, one stain and a microscope. Based on scanning electron microscopic examination of the endometrial surface, the morphologic changes peaked at estrus and diestrus phases. During estrus phase, the cells showed smooth membrane projections and depressions, hence giving the cell surface an uinblicated appearance. The so called "Pinopodes" which were considered as accurate markers for endometrial receptivity and their detection might be of high clinical utility in the preparation of endomnetrium before embryo transfer. On the other hand, during diestrus phase, the endomnetrial surface appeared flat and structurless with only some clusters of detaching apoptotic cells. In conclusion, SEM appeared to be a precious tool not only for estrous stage determination, and quantification of apoptosis but also, for monitoring endometrial maturation and timing for embryo transfer. Moreover, the present study proved that, vaginal smears stained with Methylene blue could be a good rapid method for assuring endometrial phases