Effects of adenovirus-mediated sorcin overexpression on excitation-contraction coupling in isolated rabbit cardiomyocytes

Seidler, T. et al. (2003) Effects of adenovirus-mediated sorcin overexpression on excitation-contraction coupling in isolated rabbit cardiomyocytes. Circulation Research, 93(2), pp. 132-139. (doi:10.1161/01.RES.0000081596.90205.E2)

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Abstract

To evaluate the effect of sorcin on cardiac excitation-contraction coupling, adult rabbit ventricular myocytes were transfected with a recombinant adenovirus coding for human sorcin (Ad-sorcin). A beta-galactosidase adenovirus (Ad-LacZ) was used as a control. Fractional shortening in response to 1-Hz field stimulation (at 37degreesC) was significantly reduced in Ad-sorcin-transfected myocytes compared with control myocytes (2.10 +/- 0.05% [ n = 311] versus 2.42 +/- 0.06% [ n = 312], respectively; P < 0.001). Action potential duration (at 20&DEG;C) was significantly less in the Ad-sorcin group (458 +/- 22 ms, n = 11) compared with the control group (520 +/- 19 ms, n = 10; P < 0.05). In voltage-clamped, fura 2-loaded myocytes (20degreesC), a reduced peak-systolic and end-diastolic [Ca2+](i) was observed after Ad-sorcin transfection. L-type Ca2+ current amplitude and time course were unaffected. Caffeine-induced Ca2+ release from the sarcoplasmic reticulum (SR) and the accompanying inward Na+-Ca2+ exchanger (NCX) current revealed a significantly lower SR Ca2+ content and faster Ca2+-extrusion kinetics in Ad-sorcin-transfected cells. Higher NCX activity after Ad-sorcin transfection was confirmed by measuring the NCX current-voltage relationship. beta-Escin-permeabilized rabbit cardiomyocytes were used to study the effects of sorcin overexpression on Ca2+ sparks imaged with fluo 3 at 145 to 160 nmol/L [Ca2+] using a confocal microscope. Under these conditions, caffeine-mediated SR Ca2+ release was not different between the two groups. Spontaneous spark frequency, duration, width, and amplitude were lower in sorcin-overexpressing myocytes. In summary, sorcin overexpression in rabbit cardiomyocytes decreased Ca2+-transient amplitude predominately by lowering SR Ca2+ content via increased NCX activity. The effect of sorcin overexpression on Ca2+ sparks indicates an effect on the ryanodine receptor that may also influence excitation-contraction coupling.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey and Kettlewell, Dr Sarah and Loughrey, Professor Christopher
Authors: Seidler, T., Miller, S., Loughrey, C., Kania, A., Burow, A., Kettlewell, S., Teucher, N., Wagner, S., Kogler, H., Meyers, M., Hasenfuss, G., and Smith, G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Arts > School of Critical Studies > Theology and Religious Studies
Journal Name:Circulation Research
ISSN:0009-7330

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