期刊
JOURNAL OF APPLIED PHYSIOLOGY
卷 88, 期 1, 页码 180-185出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jappl.2000.88.1.180
关键词
calcium; magnesium; binding constant; dissociation constant; actomyosin
资金
- NIAMS NIH HHS [R01AR40906] Funding Source: Medline
- NATIONAL INSTITUTE OF ARTHRITIS AND MUSCULOSKELETAL AND SKIN DISEASES [R01AR040906] Funding Source: NIH RePORTER
In contrast to previous studies, a new fluorescent method was used to accurately determine the Ca2+ concentration in test solutions used to activate skinned rat cardiac cells. This method used the calcium green-2 fluorescent indicator, which is shown to change its fluorescence over the Ca2+ range responsible for Ca2+ activation of force and ATPase. The dissociation constant (Kd) Of calcium green-2 for Ca2+ was determined for three different Mg2+ concentrations in solutions similar to those used in the experiment. Increasing Mg2+ concentration fi om 1.0 to 8.0 mM had no significant effect on the Ca2+ sensitivity of either force or actomyosin ATPase activity, in contrast to previous reported studies on force. The ATPase activity was activated at lower Ca2+ concentration than the force. The ratio (ATPase/force) is proportional to the dissociation rate of force-generating myosin cross bridges and decreased during Ca2+ activation. These findings are consistent with the hypothesis that cardiac muscle contraction is activated by a single Ca2+-specific binding site on troponin C.
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