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Defects in ryanodine receptor function are associated with systolic dysfunction in rats subjected to volume overload
Author(s) -
Juric Danijel,
Yao Xinghai,
Thandapilly Sijo,
Louis Xavier,
Cantor Elliott,
Chaze Brian,
Wojciechowski Peter,
Vasanji Zainisha,
Yang Tonghua,
Wigle Jeffrey,
Netticadan Thomas
Publication year - 2010
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2009.052100
Subject(s) - phospholamban , medicine , ryanodine receptor , pressure overload , volume overload , endocrinology , muscle hypertrophy , endoplasmic reticulum , ryanodine receptor 2 , diastole , chemistry , heart failure , biology , receptor , blood pressure , cardiac hypertrophy , biochemistry
Cardiac hypertrophy is the compensatory enlargement of the heart aimed at reducing stress induced by either pressure overload or volume overload (VO); however, sustained hypertrophy leads to cardiac dysfunction. We hypothesize that cardiac dysfunction which develops due to VO will be associated with abnormalities in sarcoplasmic reticulum (SR) function. Volume overload was induced in rats by aortocaval shunt surgery (‘VO rats’). Echocardiographic measurements were used to compare cardiac structure and function in control and VO rats. The SR was isolated from left ventricular tissue. Sarcoplasmic reticulum Ca 2+ uptake and SR Ca 2+ release were examined by the filtration method. The expression levels of SR proteins were assessed by Western immunoblotting. Rats subjected to VO developed eccentric hypertrophy. Diastolic function in VO rats was improved at all time points and was associated with elevated SR Ca 2+ uptake at 16 and 28 weeks. Sarcoendoplasmic reticulum ATPase 2a protein level was increased at 16 weeks but normalized at 28 weeks; Amounts of phospholamban protein were unaltered, but Serine16 phospholamban and Threonine17 phospholamban were reduced at 28 weeks. Systolic function was impaired in the VO rats at 16 and 28 weeks and was associated with reduced Ca 2+ release at the 28 week time point. The ryanodine receptor 2 (RyR2) protein level was reduced at 28 weeks; RyR2 phosphorylation status and the amount of FK‐binding protein 12.6 were increased at 28 weeks. On the basis of the results, we conclude that the progression of hypertrophy due to VO in rats is accompanied by the impairment of systolic function, which in turn is associated with defects in RyR2 expression and function.