Enhanced Ca2+ current and decreased Ca2+ efflux restore sarcoplasmic reticulum Ca2+ content after depletion

被引:110
作者
Trafford, AW [1 ]
Diaz, ME [1 ]
Negretti, N [1 ]
Eisner, DA [1 ]
机构
[1] UNIV LIVERPOOL,DEPT PRECLIN VET SCI,LIVERPOOL L69 3BX,MERSEYSIDE,ENGLAND
基金
英国惠康基金;
关键词
sarcoplasmic reticulum; Ca2+; Ca2+ transient;
D O I
10.1161/01.RES.81.4.477
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
[Ca2+](i) was measured using the fluorescent indicator indo 1 in voltage-clamped ferret and rat ventricular myocytes. The Ca2+ content of the sarcoplasmic reticulum (SR) was estimated from the integral of the Na+-Ca2+ exchange current activated by caffeine. Refilling of the SR after caffeine removal was enhanced by stimulation. As the systolic Ca2+ transient recovered, the integral of the L-type Ca2+ current decreased and that of the Na+-Ca2+ exchange tail current increased. For the early pulses, the gain of Ca2+ via the Ca2+ current is greater than the loss via the exchanger, and during steady state stimulation, the fluxes are equal. The difference in the integrals gives a measure of the net gain of cell Ca2+ with each pulse. When these are summed, the calculated gain of cell Ca2+ agrees well with the increase of SR Ca2+ produced by stimulation, as measured from the caffeine-evoked currents. There was a nonlinear relationship between SR Ca2+ content and the magnitude of the systolic Ca2+ transient such that at high SR Ca2+ content a given increase of content had a greater effect on the Ca2+ transient than did an increase at low SR content. In conclusion, the effects of systolic Ca2+ on the Ca2+ current and Na+-Ca2+ exchange current provide a means to regulate SR Ca2+ content and thence the systolic Ca2+ transient.
引用
收藏
页码:477 / 484
页数:8
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