Pericardial mesothelial cells produce endothelin-1 and possess functional endothelin ETB receptors

We investigated the endothelin production and endothelin receptor activity of pericardial mesothelial cells obtained from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. The pericardial mesothelial cells were maintained in vitro and the production of endothelin-1 by these cells was evaluated by using a sensitive sandwich-type enzyme immunoassay for endothelin-1 and big endothelin-1. Endothelin receptor subtypes were pharmacologically analyzed by measuring the changes of intracellular Ca2+ concentration ([Ca2+]i) in pericardial mesothelial cells. Mesothelial cells from both strains produced more immunoreactive endothelin-1 than big endothelin-1. The production of immunoreactive endothelin-1 progressively increased in a culture time-dependent manner. The amount of immunoreactive endothelin-1 detected after 72 h in pericardial mesothelial cells of SHR was significantly (P0.05) 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 endothelin-3 induced elevation of [Ca2+]i in pericardial mesothelial cells. The selective agonist of the endothelin ETB receptor, sarafotoxin S6c, also induced elevation of [Ca2+]i. The endothelin- and sarafotoxin 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 ([Cys11,Cys15]endothelin-1-(11-21)), significantly inhibited the endothelin-1- and endothelin-3-induced changes in [Ca2+]i. The endothelin ETA receptor antagonist, FR 1393171 ((R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]carbonyl]ammino -4-methylpentanoyl]amino-3-[3-(1-methyl-1H-indoyl)]propio nyl]amino-3-(2-pyridyl)propionic acid), did not affect these changes. From these results, pericardial mesothelial cells from both SHR and WKY rats shared the ability to produce endothelin-1 spontaneously in culture, although consistently greater production was detected in cultures of SHR origin. Moreover, pericardial mesothelial cells of SHR origin may have increased numbers of endothelin ETB receptors and/or a more active signal transduction system compared with those of WKY rats. These results suggest that endothelin-1 may play an important role in the pericardium in an autocrine and/or paracrine fashion.