| Summary: | 碩士 === 高雄醫學大學 === 藥理學研究所碩士班 === 95 === In pulmonary vascular smooth muscles, modulation of large-conductance Ca2+-activated K+ (BKCa) channel is important in the regulation of pulmonary arterial pressure. KMUP-1, a synthetic xanthine-based derivative, has been demonstrated to have BKCa currents activation in basilar artery myocytes.
In this study, we tried to investigate the ionic mechanisms of KMUP-1 whether and by what signaling to stimulate BKCa in pulmonary arteries. Pulmonary arterial smooth muscle cells (PASMCs) were enzymatically isolated from Sprague-Dawley rats. KMUP-1 significantly increased the BKCa current and open probability using conventional whole cell and inside-out patch-clamp techniques. Increased BKCa current activity was abolished by a BKCa channel inhibitor iberiotoxin (100 nM).
To study the mechanisms of KMUP-1 on BKCa channels, a soluble guanylate cyclase inhibitor (ODQ, 10 μM), an adenylate cyclase inhibitor (SQ22536, 10 μM), competitive antagonists of cGMP and cAMP (Rp-cGMP, 100 μM and Rp-cAMP, 100 μM), and cGMP- and cAMP-dependent protein kinase inhibitors (KT5823, 300 nM and KT5720, 300 nM) were applied. BKCa current activation by KMUP-1 was significantly inhibited by these agents. We also found that KMUP-1 has the ability to prevent uridine triphosphate (UTP, 10 μM) -induced inhibition of delayed rectifier K+ (KDR) channels. To study the relationship of KMUP-1 and RhoA/Rho kinase pathway on PASMCs, a RhoA inhibitor C3 exoenzyme (10 μg/ml), a Rho kinase (ROCK) inhibitor Y27632 (30 μM), and PKG and PKA inhibitors (KT5823, 300 nM and KT5720, 300 nM) were applied.
In conclusion, KMUP-1 increases the BKCa current and channel open probability by stimulating the activity of cyclic nucleotide-dependent protein kinases. Additionally, KMUP-1 also inhibits the RhoA/ROCK pathway would result in the relaxation of pulmonary arteries.
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