The endothelin system in human and monkey ovaries: in situ gene expressionof the different components

The endothelin system is composed of three endothelin isoforms (ET-1, ET-2, and ET-3), the endothelin receptors ETA and ETB, and the endothelin-conver ting enzyme (ECE). Besides having a major vasoactive role, endothelins have roles in different cell types at a local level. We investigated the presen ce of the different components of the endothelin system in primate ovaries. Human Introduction ovaries and gonadotropin-stimulated monkey ovaries were studied using immunohistochemistry for endothelin, and in situ hybridizati on with probes for ET-1, ET-2, ET-3, ETA and ETB receptors, and ECE. ET-1 a nd ETA receptors were detected in endothelial cells and vascular smooth mus cle cells, respectively, in stromal vessels adjacent to follicles and corpo ra lutea. ETB receptors and ET-1 were found in the endothelial cells of cap illaries of corpora lutea. ECE was present in internal theca cells of secon dary, de Graaf, atretic follicles, and in luteinized granulosa cells of the corpora lutea. The endothelin system components are present in or around t he follicles of human and monkey ovaries. Although the components are not e xpressed in the same cell types, they are synthesized, mainly in follicles, by cells that are in close proximity. Thus, the endothelin system could ac t in a paracrine manner. ECE expression in steroid-producing cells changes its compartmentalization during follicle maturation.