Selective down-regulation of sub-endocardial ryanodine receptor expression in a rabbit model of left ventricular dysfunction.
Defective sarcoplasmic reticulum (SR) Ca2+ handling is evident in cardiomyopathy and may be mediated by selective dysregulation of SR Ca2+ handling proteins. To assess whether regulation of SR Ca2+ release may vary regionally within the normal and diseased heart, left ventricular transmural expression and activity of the ryanodine receptor (RyR2) was studied in a rabbit coronary artery ligation model of left ventricular dysfunction (LVD). Tissue/cells were isolated from both the sub-endocardial and subepicardial layers of the left ventricular free wall from sham-operated and coronary artery ligated rabbit hearts. Three independent methods were used to study alterations in RyR2 mRNA (real-time quantitative PCR (RT-PCR)) and protein expression (quantitative immunoblotting and [3H] ryanodine binding). These biochemical data were compared with functional measurements of fractional SR Ca2+ release from both of these regions. Data from RT-PCR revealed lower RyR2 mRNA levels in the sub-endocardium compared with subepicardium in both experimental groups with the reduction being significantly lower in the sub-endocardium from the LVD group. Quantitative analysis of RyR2 protein levels revealed the same expression patterns. Calsequestrin mRNA and protein levels showed no significant changes. This study demonstrates a lower expression level of RyR2 in the sub-endocardium of the left ventricle of rabbit hearts and is the first to show a further specific reduction in LVD. There is a corresponding decrease in fractional SR Ca2+ release in cells isolated from the sub-endocardium of hearts from the LVD group, relating these selective biochemical alterations to changes in function.
Currie
Susan
S
Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK. s.currie@strath.ac.uk
Quinn
F Russell
FR
Sayeed
Rana A
RA
Duncan
Alexis M
AM
Kettlewell
Sarah
S
Smith
Godfrey L
GL
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002155:Calsequestrin / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation; D004699:Endocardium / Q000378:metabolism*; D008297:Male; D011485:Protein Binding; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics* / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D018487:Ventricular Dysfunction, Left / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology*
D002155:Calsequestrin; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine