Endothelin receptor expression in human decidua

The endothelins are signalling peptides that act via two receptors, ET(A)and ET(B). In the human endometrium, endothelin receptors have beendemonstrated in glands and stroma and have been shown to vary during thecourse of the menstrual cycle. The present study was undertaken todetermine whether or not expression of endothelin receptors changes duringpregnancy or after administration of exogenous progestagens. The expressionof the receptors was correlated with the appearance of basement membranecomponents during decidualization of the endometrial stroma. Decidualspecimens (n = 15) were obtained during the first trimester of pregnancyand 10 at term. Sixteen pairs of endometrial biopsies were obtained fromwomen with menorrhagia before and after exposure to exogenous progestagens.A total of 15 hysterectomy specimens were used as controls for theexpression of stromal basement membrane proteins in the absence ofdecidualization. Autoradiography was carried out with selective ligands forET(A) ([125I]-PD 151242) and ET(B) ([125I]-BQ3020). The distribution ofligand binding was then compared with the distribution of laminin alpha2light chain and collagen IV. ET(A), ET(B), laminin alpha2 light chain, andcollagen IV were expressed in stromal decidual cells in the first trimesterof pregnancy. ET(B) was also found on endometrial glandular epithelium.Quantitative macro-autoradiography and multiple regression analysisdemonstrated a highly significant positive correlation (P < 0.001)between expression of ET(B) and laminin alpha2 light chain. In the thirdtrimester qualitative examination suggested a reduction of ET(A) in thestroma. Progestagen-induced decidua exhibited a similar pattern to thatfound in first trimester decidua. This study has demonstrated up-regulationof ET(B) during the progesterone- dependent process of decidualization andsuggests a paracrine or autocrine role for endothelins in the decidua.