Ryanodine receptors are uncoupled from contraction in rat vena cava

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• 作者：N.R. Tykocki ; ^{tykockin@msu.edu} ; J.M. Thompson ; W.F. Jackson ; S.W. Watts
• 关键词：Ryanodine receptor ; Vascular smooth muscle ; Vasoconstriction ; Veins ; Calcium ; Sarcoplasmic reticulum
• 刊名：Cell Calcium
• 出版年：2013
• 出版时间：February, 2013
• 年：2013
• 卷：53
• 期：2
• 页码：112-119
• 全文大小：938 K

文摘

Ryanodine receptors (RyR) are Ca²⁺-sensitive ion channels in the sarcoplasmic reticulum (SR) membrane, and are important effectors of SR Ca²⁺ release and smooth muscle excitation-contraction coupling. While the relationship between RyR activation and contraction is well characterized in arteries, little is known about the role of RyR in excitation-contraction coupling in veins. We hypothesized that RyR are present and directly coupled to contraction in rat aorta (RA) and vena cava (RVC). RA and RVC expressed mRNA for all 3 RyR subtypes, and immunofluorescence showed RyR protein was present in RA and RVC smooth muscle cells. RA and RVC rings contracted when Ca²⁺ was re-introduced after stores depletion with thapsigargin (1 ¦ÌM), indicating both tissues contained intracellular Ca²⁺ stores. To assess RyR function, contraction was then measured in RA and RVC exposed to the RyR activator caffeine (20 mM). In RA, caffeine caused contraction that was attenuated by the RyR antagonists ryanodine (10 ¦ÌM) and tetracaine (100 ¦ÌM). However, caffeine (20 mM) did not contract RVC. We next measured contraction and intracellular Ca²⁺ (Ca²⁺_i) simultaneously in RA and RVC exposed to caffeine. While caffeine increased Ca²⁺_i and contracted RA, it had no significant effect on Ca²⁺_i or contraction in RVC. These data suggest that ryanodine receptors, while present in both RA and RVC, are inactive and uncoupled from Ca²⁺ release and contraction in RVC.