Endothelin-1 (Et) has profound effects on glomerular microcirculation and mesangial cell contraction. A parameter of mesangial cell contraction was examined by measuring myosin light chain phosphorylation (MLCP) in glomerular mesangial cells in the presence and absence of a newly developed endothelin-1 receptor antagonist (EtA). Addition of Et alone (10 nM) caused a marked increase in MLCP, which, on average, rose by 53 ± 6% above the level in cells exposed to vehicle (P < 0.0005). This effect was shown to continue for at least one hour; MLCP at 60 minutes was 64 ± 12% higher than controls, (P < 0.025), constituting a unique observation of an in vitro parameter which parallels the characteristic in vivo effect of Et. Treatment of cells with EtA virtually abolished this Et-induced increase in MLCP, which rose by only 2 ± 3% and - 1 ± 4% for doses of EtA of 44 nM and 66 nM, respectively. Examination of the intracellular calcium concentration, [Ca2+]i, revealed that EtA almost completely abolished the transient increase in [Ca2+]i evoked by Et and also suppressed the early portions of the sustained increase in [Ca2+]i. EtA was ineffective in abolishing [Ca2+]i increase in response to arginine vasopressin. Finally, to evaluate EtA's efficacy in a pathophysiologic setting, we also studied mesangial cells exposed to cyclosporine (Cs). Exposure of mesangial cells to Cs (10-5 M) for 60 minutes caused a significant increase in MLCP, on average, by 38 ± 6% above control (P < 0.0005), while cells exposed to Cs in the presence of EtA increased MLCP significantly less, by only 15 ± 9%. These data provide further evidence for Et's long-lasting cellular actions, and demonstrate inhibitory effects of an Et receptor antagonist after direct cellular exposure to Et and also after Cs exposure, a pathophysiologic setting which likely involves Et.
CITATION STYLE
Takeda, M., Breyer, M. D., Noland, T. D., Homma, T., Hoover, R. L., Inagami, T., & Kon, V. (1992). Endothelin-1 receptor antagonist: Effects on endothelin- and cyclosporine-treated mesangial cells. Kidney International, 41(6), 1713–1719. https://doi.org/10.1038/ki.1992.245
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