Localization of bradykinin type II receptor mRNA in human endometrium

Bradykinin is a nonapeptide inflammatory agent that in the endometrium stimulates stromal cell proliferation, prostaglandin synthesis and electrogenic ion transport. The expression of bradykinin type II (B2) receptor mRNA was examined by in-situ hybridization using 35S-labelled riboprobe in human endometrium to determine its temporal and spatial pattern of distribution throughout the menstrual cycle. The B2 receptor mRNA was expressed in proliferative and secretory endometrium. In the early proliferative endometrium there were low levels of B2 receptor mRNA over both the glands and stromal cells. The signal increased in intensity and was localized over the glands with low levels of hybridization in the stroma in the late proliferative endometrium. In the early secretory endometrium B2 receptor mRNA was highly expressed in the endometrial glands. The strong hybridization signal persisted and in late secretory endometrium both glandular and stromal cells expressed B2 receptor mRNA. The apparent increase in B2 receptor mRNA in the secretory endometrium suggests that bradykinin acting via B2 receptor may play a role in the increased vascular permeability and vasodilatation associated with implantation.