Pericardial mesothelial cells produce endothelin-1 and possess functional endothelin ET B receptors

Abstract

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 Ca 2+ concentration ([Ca 2+] 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 ( 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 endothelin-3 induced elevation of [Ca 2+] i in pericardial mesothelial cells. The selective agonist of the endothelin ET B receptor, sarafotoxin S6c, also induced elevation of [Ca 2+] i . The endothelin- and sarafotoxin S6c-induced elevations of [Ca 2+] i in pericardial mesothelial cells from SHR were greater than those in mesothelial cells from WKY rats. The endothelin ET B receptor antagonist, IRL 1038 ([Cys 11,Cys 15]endothelin-1-(11-21)), significantly inhibited the endothelin-1- and endothelin-3-induced changes in [Ca 2+] i . The endothelin ET A receptor antagonist, FR1393171 (( R)2-[( R)-2-[( S)-2-[[1-(hexahydro-1 H-azepinyl)]carbonyl]ammino-4-methylpentanoyl]amino-3-[3-(1-methyl-1 H-indoyl)]propionyl]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 ET B 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.