Distribution and characteristics of mast cells in the rat ovary during the oestrous cycle, lactation and pregnancy.

Changes in the number and distribution of the mast cells were studied in rat ovaries during the oestrous cycle, pregnancy and lactation. Mast cells were present in the hilum and stroma, the wall of atretic follicles and the corpora lutea. The total number of cells was high during oestrus and metoestrus and significantly lower during dioestrus and pro-oestrus. The mast cell counts in pregnant and lactating rats were lower than during the oestrous cycle. The number of mast cells was highest in the hilum, in all the given reproductive states. During oestrus and pregnancy there were more compact cells than degranulating cells, but during lactation the number of degranulating cells per ovarian section was higher. These variations of mast cell numbers in different reproductive states suggest that the mast cells play a significant role in ovarian activity.