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Publication : Dilated cardiomyopathy with increased SR Ca2+ loading preceded by a hypercontractile state and diastolic failure in the alpha(1C)TG mouse.

First Author  Wang S Year  2009
Journal  PLoS One Volume  4
Issue  1 Pages  e4133
PubMed ID  19125184 Mgi Jnum  J:145154
Mgi Id  MGI:3833764 Doi  10.1371/journal.pone.0004133
Citation  Wang S, et al. (2009) Dilated cardiomyopathy with increased SR Ca2+ loading preceded by a hypercontractile state and diastolic failure in the alpha(1C)TG mouse. PLoS One 4(1):e4133
abstractText  Mice over-expressing the alpha(1)_subunit (pore) of the L-type Ca2+ channel (alpha(1C)TG) by 4 months (mo) of age exhibit an enlarged heart, hypertrophied myocytes, increased Ca2+ current and Ca2+ transient amplitude, but a normal SR Ca2+ load. With advancing age (8-11 mo), some mice demonstrate advanced hypertrophy but are not in congestive heart failure (NFTG),while others evolve to frank dilated congestive heart failure (FTG). We demonstrate that older NFTG myocytes exhibit a hypercontractile state over a wide range of stimulation frequencies, but maintain a normal SR Ca2+ load compared to age matched non-transgenic (NTG) myocytes. However, at high stimulation rates (2-4 Hz) signs of diastolic contractile failure appear in NFTG cells. The evolution of frank congestive failure in FTG is accompanied by a further increase in heart mass and myocyte size, and phospholamban and ryanodine receptor protein levels and phosphorylation become reduced. In FTG, the SR Ca2+ load increases and Ca2+ release following excitation, increases further. An enhanced NCX function in FTG, as reflected by an accelerated relaxation of the caffeine-induced Ca2+ transient, is insufficient to maintain a normal diastolic Ca2+ during high rates of stimulation. Although a high SR Ca2+ release following excitation is maintained, the hypercontractile state is not maintained at high rates of stimulation, and signs of both systolic and diastolic contractile failure appear. Thus, the dilated cardiomyopathy that evolves in this mouse model exhibits signs of both systolic and diastolic failure, but not a deficient SR Ca2+ loading or release, as occurs in some other cardiomyopathic models.
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