Temporospatial changes of kinin B2 receptors during the estrous cycle and pregnancy in the rat uterus

Tissue kallikreins are present in rat uterus during the estrous cycle in lu minal and glandular epithelium, in early gestation in the implantation node , and in the last third of pregnancy surrounding the sinusoids in the decid ua basalis. The pattern of kinin B2 receptor expression, through which the vasoactive effect of kallikreins is exerted, was studied by in vitro autora diography and immunohistochemistry. The kinin B2 receptor was observed in t he luminal and glandular epithelium, myometrium, endothelial cells of arter ies, veins and venules, and smooth muscle cells of endometrial and myometri al arterioles. Immunoblotting of crude membranes revealed a band of 69 kDa that increased in late proestrus and estrus, concordantly with the pattern of immunostaining observed in the tissue. At Day 7 of gestation, the kinin B2 receptor was expressed (binding sites and receptor protein) in the epith elium of the implantation node and decidual cells; these latter cells showe d a further increase during gestational Days 9 and 10. From Days 14 to 21, the subplacental decidua became strongly immunoreactive, and on Days 16 and 21 the placental labyrinthine endothelium was intensely stained. During th is period, endothelium of arteries and veins, smooth muscular cells of smal l diameter arterioles, and myometrium also expressed B2 receptors. In unila terally oil-stimulated pseudopregnancy, the decidual cells and the glandula r epithelium show similar immunoreactivity to that during pregnancy. The te mporospatial pattern of kinin B2 receptors, coinciding with that of kallikr ein or with sites accessible to the generated kinins, further supports an a utocrine-paracrine role for the kallikreinkinin system in the vasoactive ch anges of implantation and placental blood flow regulation.