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Targeted overexpression of the sarcoplasmic reticulum Ca2+-ATPase increases cardiac contractility in transgenic mouse hearts.

Authors: Baker, DL  Hashimoto, K  Grupp, IL  Ji, Y  Reed, T  Loukianov, E  Grupp, G  Bhagwhat, A  Hoit, B  Walsh, R  Marban, E  Periasamy, M 
Citation: Baker DL, etal., Circ Res. 1998 Dec 14-28;83(12):1205-14.
Pubmed: (View Article at PubMed) PMID:9851937

Cardiac hypertrophy and heart failure are known to be associated with a reduction in Ca2+-ATPase pump levels of the sarcoplasmic reticulum (SR). To determine whether, and to what extent, alterations in Ca2+ pump numbers can affect contraction and relaxation parameters of the heart, we have overexpressed the cardiac SR Ca2+-ATPase specifically in the mouse heart using the alpha-myosin heavy chain promoter. Analysis of 2 independent transgenic lines demonstrated that sarco(endo)plasmic reticulum Ca2+-ATPase isoform (SERCA2a) mRNA levels were increased 3.88+/-0. 4-fold and 7.90+/-0.2-fold over those of the control mice. SERCA2a protein levels were increased by 1.31+/-0.05-fold and 1.54+/-0. 05-fold in these lines despite high levels of mRNA, suggesting that complex regulatory mechanisms may determine the SERCA2a pump levels. The maximum velocity of Ca2+ uptake (Vmax) was increased by 37%, demonstrating that increased pump levels result in increased SR Ca2+ uptake function. However, the apparent affinity of the SR Ca2+-ATPase for Ca2+ remains unchanged in transgenic hearts. To evaluate the effects of overexpression of the SR Ca2+ pump on cardiac contractility, we used the isolated perfused work-performing heart model. The transgenic hearts showed significantly higher myocardial contractile function, as indicated by increased maximal rates of pressure development for contraction (+dP/dt) and relaxation (-dP/dt), together with shortening of the normalized time to peak pressure and time to half relaxation. Measurements of intracellular free calcium concentration and contractile force in trabeculae revealed a doubling of Ca2+ transient amplitude, with a concomitant boost in contractility. The present study demonstrates that increases in SERCA2a pump levels can directly enhance contractile function of the heart by increasing SR Ca2+ transport.

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CRRD Object Information
CRRD ID: 10047146
Created: 2015-07-11
Species: All species
Last Modified: 2015-07-11
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.