Cellular mechanisms and role of endothelin-1-induced calcium oscillations in pulmonary arterial myocytes

Abstract

The effect of endothelin (ET)-1 on both cytosolic Ca2+ concentration ([Ca2+]i) and membrane current in freshly isolated myocytes, as well as on the contraction of arterial rings, was investigated in rat main pulmonary artery (RMPA) and intrapulmonary arteries (RIPA). ET-1 (5–100 nM, 30 s) induced a first [Ca2+]ipeak followed by 3–5 oscillations of decreasing amplitude. In RMPA, the ET-1-induced [Ca2+]iresponse was fully abolished by BQ-123 (0.1 μM). In RIPA, the response was inhibited by BQ-123 in only 21% of the cells, whereas it was abolished by BQ-788 (1 μM) in 70% of the cells. In both types of arteries, the response was not modified in the presence of 100 μM La3+ or in the absence of external Ca2+ but disappeared after pretreatment of the cells with thapsigargin (1 μM) or neomycin (0.1 μM). In RPMA myocytes clamped at −60 mV, ET-1 induced an oscillatory inward current, the reversal potential of which was close to the equilibrium potential for Cl−. This current was unaltered by the removal of external Ca2+ but was abolished by niflumic acid (50 μM). In arterial rings, the ET-1 (100 nM)-induced contraction was decreased by 35% in the presence of either niflumic acid (50 μM) or nifedipine (1 μM). These results demonstrate that ET-1 via the ETA receptor only in RMPA and both ETA and ETB receptors in RIPA induce [Ca2+]ioscillations due to iterative Ca2+release from an inositol trisphosphate-sensitive Ca2+ store. Ca2+ release secondarily activates an oscillatory membrane Cl−current that can depolarize the cell membrane, leading to an influx of Ca2+, this latter contributing to the ET-1-induced vasoconstrictor effect.

The Cl− channel blocker niflumic acid releases Ca2+ from an intracellular store in rat pulmonary artery smooth muscle cells

“…A similar effect has been observed with NPPB on vasopressin-induced [Ca 2 þ ] i transients in A7r5 cells (Pon et al, 1993). However, in contrast to these studies, NFA (50 mM) has been shown to have no effect on the endothelin-1-induced Ca 2 þ oscillations in freshly isolated rat PASMCs (Hyvelin et al, 1998), or on the 5-HT-induced [Ca 2 þ ] i transients in cultured rat PASMCs (Yuan, 1997).…”

“…Despite a large number of studies examining the effect of Cl À channel blockers on the contractile and electrophysiological properties of smooth muscle, there have been very few studies that systematically look at the effect of these drugs on intracellular Ca 2 þ signalling (Pon et al, 1993;Yuan, 1997;Hyvelin et al, 1998). Thus, the objective of the present study was to determine the effect of four different Cl À channel blockers on caffeine-induced Ca 2 þ signalling in rat pulmonary artery smooth muscle cells (PASMCs).…”

“…Specifically, the Cl À channel blocker niflumic acid (NFA) has been shown to reduce the magnitude of agonist-induced contractions in the rat aorta (Criddle et al, 1996;Lamb & Barna, 1998) and pulmonary artery (Wang et al, 1997;Yuan, 1997;Hyvelin et al, 1998), as well as the rabbit basilar (Uchida et al, 1990) and middle cerebral arteries (Gokina & Bevan, 2000). Other Cl À channel blockers including 4,4 0 -diisothiocyanatostilbene-2,2 0 -disulfonic acid (DIDS) and anthracene-9-carboxylic acid (A-9-C) have been shown to have similar inhibitory effects on vascular smooth muscle contraction (Lamb & Barna, 1998;Gokina & Bevan, 2000).…”

Potassium-induced intermittent vasomotion in rat isolated pulmonary artery

“…In myocytes of rat main pulmonary artery, oscillation in intracellular Ca 2+ is presumed to be linked to vasomotion, with extracellular Ca 2+ making a very limited contribution (Hyvelin et al, 1998). As shown in the present investigation, vasomotion in the same blood vessel displays a higher order slow periodicity which does not appear to have been reported previously.…”

“…Accordingly, a functional SR would appear necessary for generating this pattern. Cycling and release of intracellular Ca 2+ are deemed to be necessary for vasomotion (Hyvelin et al, 1998;Haddock et al, 2002). Lee and colleagues (2001) waves.…”