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Ryanodine receptors are uncoupled from contraction in rat vena cava.

ABSTRACT: Ryanodine receptors (RyR) are Ca(2+)-sensitive ion channels in the sarcoplasmic reticulum (SR) membrane, and are important effectors of SR Ca(2+) 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 Ca(2+) was re-introduced after stores depletion with thapsigargin (1?M), indicating both tissues contained intracellular Ca(2+) stores. To assess RyR function, contraction was then measured in RA and RVC exposed to the RyR activator caffeine (20mM). In RA, caffeine caused contraction that was attenuated by the RyR antagonists ryanodine (10?M) and tetracaine (100?M). However, caffeine (20mM) did not contract RVC. We next measured contraction and intracellular Ca(2+) (Ca(2+)(i)) simultaneously in RA and RVC exposed to caffeine. While caffeine increased Ca(2+)(i) and contracted RA, it had no significant effect on Ca(2+)(i) or contraction in RVC. These data suggest that ryanodine receptors, while present in both RA and RVC, are inactive and uncoupled from Ca(2+) release and contraction in RVC.

SUBMITTER: Tykocki NR

PROVIDER: S-EPMC4049347 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Ryanodine receptors are uncoupled from contraction in rat vena cava.

Tykocki N R NR Thompson J M JM Jackson W F WF Watts S W SW

Cell calcium 20121122 2

Ryanodine receptors (RyR) are Ca(2+)-sensitive ion channels in the sarcoplasmic reticulum (SR) membrane, and are important effectors of SR Ca(2+) 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 ...[more]

PMID: 23177664

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Project description:While blood vessels have muscular walls that undergo tonic contractions to alter vascular resistance and, thus, control blood flow, lymphatics at the level of the collecting vessels and higher have muscular walls capable of rapid phasic contractions that generate lymph flow in addition to tonic contractions that regulate lymph flow resistance. While the ability of lymphatics to undergo rapid phasic contractions has been known for several centuries, the biological elements governing this phenomenon remain unknown. In an attempt to gain insight into the structural and regulatory elements that give lymphatic vessels their unique contractile capabilities, we utilized two-color microarray analysis to compare the thoracic duct of the rat to the vena cava of the same donor animal. Total cellular RNA was isolated immediately following vessel isolation and amplified in the presence of amino allyl dUTP. The resulting modified aRNA was conjugated to either Cy3 or Cy5 dye prior to hybridization to a rat 5.7K oligonucleotide array. Analysis and filtering of the data obtained from the microarray image yielded several contractile and regulatory genes with altered expression in the thoracic duct relative to the vena cava. Further evaluation of the data obtained in this study may aid in illustrating the unique properties of the lymphatic vessel and its muscular wall. Keywords: Thoracic duct, lymphatics, microarray Four unique thoracic duct/vena cava sample pairs were individually analyzed via two-color microarray analysis yielding 4 biological replicates. To minimize dye bias, a dye balance design was utilized in which the orientation of dye assignment was alternated between vessel pairs (i.e. two thoracic duct samples were labeled with Cy3 and two were labeled with Cy5). Prior to analysis, the data from 2 of the replicates was transformed to accomodate the dye balance such that all thoracic duct data is interpreted as Cy5 and all vena cava data is interpreted as Cy3.

Dataset Information

Ryanodine receptors are uncoupled from contraction in rat vena cava.

Publications

Ryanodine receptors are uncoupled from contraction in rat vena cava.

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