MORPHOLOGICAL-STUDY OF THE CORPUS-LUTEUM IN THE RAT

The cyclic related growth and regression of the corpus luteum during four consecutive oestrous cycles of the regular four-day-cycling (ie, 16 days), virgin albino Wistar rat were followed up by light and electron microscopic investigation of the ovaries. After ovulation, follicular granulosa cells differentiated into luteal cells in the newly formed corpus luteum. Based on their specific histological characteristics, four various types of corpus luteum in each stage of the oestrous cycle could be identified. As soon as the luteal cells started to degenerate, the number of fibroblasts progressively increased and apoptotic degeneration of luteal cells was initiated and became most prominent during oestrus. Complete regression of the corpus luteum was seen after 15 days. This study shows a strictly organised pattern of luteal cell growth and degeneration in the corpus luteum of the regular four-day-cycling, virgin Wistar rat. The morphological alterations may be regulated by a hormonal fluctuation.