Estrous cycle-related changes in mast cell numbers in several ovarian compartments in the rat

The absolute number of mast cells in several ovarian compartments was studied during the estrous cycle of the rat. The number of mast cells significantly increased on proestrus (either in the morning or in the evening) in the ovarian medulla and cortex, whereas no significant changes were found in the ovarian bursa. During proestrus, abundant mast cells were present in the bursal cavity along with eosinophil and mononuclear leucocytes. Mast cells in the different ovarian compartments corresponded to mature mast cells, and degranulated or immature cells were only rarely found. These results seem to indicate that migration from an extraovarian source could be the mechanism underlying cyclic changes in ovarian mast cells.