Aim: Female sex hormones have long been suspected to have an effect on mast cell (MC) behavior. Based on this idea, we determined MC content in reproductive tract throughout the estrus cycle by using histochemical techniques.

Materials and Methods: Genital tracts of 23 healthy cows were collected from a local slaughterhouse. The animals were classified into two groups as follicular phase (n=13) and luteal phase (n=10). The tissue samples were taken and fixed in formaldehyde- alcohol solution (FA). Then, histological sections of 5-6 μm thickness were prepared and stained by toluidin blue and alcian blue/safranin O methods.

Results: Mast cells (MCs) demonstrated metachromatic staining properties with toluidine blue. MCs were not observed in the follicle of theca interna, and corpus luteum of the ovary and, surface epithelium of the reproductive organs. MCs generally associated with blood vessels in all samples. Three types of cells, including AB() cells with blue cytoplasm, pink-red coloured SO (+) cells and blue-pink coloured AB/SO(+) cells were indicated by AB/SO staining in the reproductive organs. There was a difference in the number of MCs between the follicular and luteal phases of the estrus cycle (P<0.05).

Conclusions: This study showed histomorphometrical changes of mast cells in the bovine reproductive tract in both follicular and luteal phases of estrus cycle. We suggest that further studies related to structures and granular contents of MCs should be sustained in all parts of genital systems in order to understand possible roles of MCs in mechanisms of unknown causes of infertility.