Calcium mobilization is required for peroxynitrite-mediated enhancement of spontaneous transient outward currents in arteriolar smooth muscle cells.
Transiently local release of Ca(2+) from the sarcoplasmic reticulum (SR) activates nearby Ca(2+)-activated K(+) channels to produce spontaneous transient outward currents (STOCs) in smooth muscle cells. The purpose of the present study was to investigate the possible effect of peroxynitrite (ONOO(-)) on STOCs in mesenteric arteriolar smooth muscle cells (ASMCs) and decide whether Ca(2+) mobilization was involved in STOCs alteration by ONOO(-). STOCs were recorded and characterized using the perforated whole-cell patch-clamp configuration. The results demonstrated that STOCs activity was greatly suppressed by removal of extracellular Ca(2+); by addition of nifedipine, a specific inhibitor of L-type voltage-gated Ca(2+) channels (VGCCs); or by addition of ryanodine, a SR ryanodine receptors (RyRs) blocker. In contrast, both caffeine, a RyR activator, and 2-aminoethoxydiphenylborate (2-APB), a membrane-permeable inositol 1,4,5-trisphosphate receptors, (IP3R) antagonist, increased STOCs activity. 3-morpholinosydnonimine (SIN-1), an ONOO(-) donor, at concentrations of 20-200 microM, induced a dose-dependent enhancement of STOCs in ASMCs and led to conspicuous increases in STOCs frequency and amplitude, which were prevented by prior exposure to low external Ca(2+) (200 nM), ryanodine (10 microM), or nifedipine (10 microM). In contrast, caffeine (0.5 mM) did not further stimulate STOCs in ASMCs preincubated with SIN-1, and pretreatment with 2-APB (50 microM) had little effect on ONOO(-) -induced STOCs activation. These findings suggest that complex Ca(2+)-mobilizing pathways, including external Ca2+ influx through VGCCs activation and subsequent internal Ca(2+) release through RyRs but not IP3Rs, are involved in ONOO(-)mediated STOCs enhancement in ASMCs.
Pan
Bing-Xing
BX
Department of Pathophysiology, First Military Medial University, Guangzhou 510515, People's Republic of China.
Zhao
Gui-Ling
GL
Huang
Xu-Liang
XL
Zhao
Ke-Seng
KS
D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D008297:Male; D008564:Membrane Potentials; D008954:Models, Biological; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009130:Muscle, Smooth / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D030421:Peroxynitrous Acid / Q000737:chemistry / Q000494:pharmacology*; D011188:Potassium / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D012433:Ryanodine / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors
D001896:Boron Compounds; D030421:Peroxynitrous Acid; D012433:Ryanodine; D002110:Caffeine; C002385:linsidomine; D008981:Molsidomine; C109986:2-aminoethoxydiphenyl borate; D009543:Nifedipine; D011188:Potassium; D002118:Calcium