Effect of oestradiol on mast cell number and histamine level in the mammary glands of rat.

Variations of mast cell number, histamine concentration and oestrogen receptor (ER) expression in mammary glands with the fluctuation of plasma oestradiol level were identified either in the intact rats at different oestrous stages or in the ovary-ectomized rats administrated with different doses of oestradiol benzoate. The results showed that the number of mast cells and histamine concentration fluctuated concomitantly with plasma oestradiol level during the oestrous cycle. More mast cell number and higher histamine concentrations were observed in the oestrous stage than that in the prooestrous and dioestrous stages. Ovariectomy decreased the mast cell number and histamine concentration, which were reconstituted by exogenous oestradiol. ER was mainly found in the nuclear of epithelial cells and interstitial cells of mammary glands. In addition, ER was also expressed in the cytoplasm of some stromal cells. These stromal cells were verified to be mast cells. In conclusion, our results suggested that oestradiol modulated mast cell number and its degranulation in the mammary gland through the ERs pathway.