Endothelin (ET-1, -2, and -3 designate three genes which produce different endothelin isopeptides) is a prolactin inhibiting substance of hypothalmic origin. ET-1 binding is part of at least four G protein signaling pathways in lactotrophs. The sequence of events in these pathways following the presentation of nano- and pico-molar concentrations of ET-1 is modeled in the paper.
Bertram R, Tabak J, Toporikova N, Freeman ME (2006) Endothelin action on pituitary lactotrophs: one receptor, many GTP-binding proteins. Sci STKE 2006:pe4 [PubMed]