PERICARDIAL MESOTHELIAL CELLS PRODUCE ENDOTHELIN-1 AND POSSESS FUNCTIONAL ENDOTHELIN ETB RECEPTORS

We investigated the endothelin production and endothelin receptor acti vity of pericardial mesothelial cells obtained from spontaneously hype rtensive rats (SHR) and Wistar-Kyoto (WKY) rats. The pericardial mesot helial cells were maintained in vitro and the production of endothelin -1 by these cells was evaluated by using a sensitive sandwich-type enz yme immunoassay for endothelin-1 and big endothelin-1. Endothelin rece ptor subtypes were pharmacologically analyzed by measuring the changes of intracellular Ca2+ concentration ([Ca2+](i)) in pericardial mesoth elial cells. Mesothelial cells from both strains produced more immunor eactive endothelin-1 than big endothelin-1. The production of immunore active endothelin-1 progressively increased in a culture time-dependen t manner. The amount of immunoreactive endothelin-1 detected after 72 h in pericardial mesothelial cells of SHR was significantly (P < 0.05) higher than that in the cells of WKY rats (SHR: 196.7 +/- 19.1 pg/10( 6) cells; WKY: 122.7 +/- 10.6 pg/10(6) cells). Endothelin-1 and endoth elin-3 induced elevation of [Ca2+](i) in pericardial mesothelial cells . The selective agonist of the endothelin ETB receptor, sarafotoxin S6 c, also induced elevation of [Ca2+](i). The endothelin- and sarafotoxi n S6c-induced elevations of [Ca2+](i) in pericardial mesothelial cells from SHR were greater than those in mesothelial cells from WKY rats. The endothelin ETB receptor antagonist, IRL 1038 ([Cys(11),Cys(15)]end othelin-1-(11-21)), significantly inhibited the endothelin-1- and endo thelin-3-induced changes in [Ca2+](i). The endothelin ETA receptor ant agonist, FR1393171 -1H-indoyl)]propionyl]amino-3-(2-pyridyl)propionic acid), did not affect these changes. From these results, pericardial m esothelial cells from both SHR and WKY rats shared the ability to prod uce endothelin-1 spontaneously in culture, although consistently great er production was detected in cultures of SHR origin. Moreover, perica rdial mesothelial cells of SHR origin may have increased numbers of en dothelin ETB receptors and/or a more active signal transduction system compared with those of WKY rats. These results suggest that endotheli n-1 may play an important role in the pericardium in an autocrine and/ or paracrine fashion. (C) 1998 Elsevier Science B.V.