Characteristics of phosphate-induced Ca(2+) efflux from the SR in mechanically skinned rat skeletal muscle fibers |
| |
Authors: | Duke A M Steele D S |
| |
Affiliation: | Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA. |
| |
Abstract: | ATP is a candidate enteric inhibitory neurotransmitterin visceral smooth muscles. ATP hyperpolarizes visceral muscles via activation of small-conductance, Ca2+-activatedK+ (SK) channels. Coupling between ATP stimulation and SKchannels may be mediated by localized Ca2+ release.Isolated myocytes of the murine colon produced spontaneous, localizedCa2+ release events. These events corresponded tospontaneous transient outward currents (STOCs) consisting ofcharybdotoxin (ChTX)-sensitive and -insensitive events.ChTX-insensitive STOCs were inhibited by apamin. LocalizedCa2+ transients were not blocked by ryanodine, but theseevents were reduced in magnitude and frequency by xestospongin C(Xe-C), a blocker of inositol 1,4,5-trisphosphate receptors. Thus wehave termed the localized Ca2+ events in colonic myocytes"Ca2+ puffs." The P2Y receptor agonist2-methylthio-ATP (2-MeS-ATP) increased the intensity and frequency ofCa2+ puffs. 2-MeS-ATP also increased STOCs in associationwith the increase in Ca2+ puffs.Pyridoxal-phospate-6-azophenyl-2',4'-disculfonic acid tetrasodium, aP2 receptor inhibitor, blocked responses to 2-MeS-ATP. Spontaneous Ca2+ transients and the effects of 2-MeS-ATP onCa2+ puffs and STOCs were blocked by U-73122, an inhibitorof phospholipase C. Xe-C and ryanodine also blocked responses to2-MeS-ATP, suggesting that, in addition to release from IP3receptor-operated stores, ryanodine receptors may be recruited duringagonist stimulation to amplify release of Ca2+. These datasuggest that localized Ca2+ release modulatesCa2+-dependent ionic conductances in the plasma membrane.Localized Ca2+ release may contribute to the electricalresponses resulting from purinergic stimulation. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
| 点击此处可从《American journal of physiology. Cell physiology》浏览原始摘要信息 |
|
点击此处可从《American journal of physiology. Cell physiology》下载全文 |
|