Solov'eva O E, Markhasin V S, Tsyv'ian P B, Keller B B
Yekaterinburg Filial Institute of Physiology, Ural Division, Russian Academy of Sciences, Russia.
Biofizika. 1999 Mar-Apr;44(2):337-49.
The force-interval relationship was studied on myocardium preparations from chick embryos and hatched chickens. It is shown that the force-interval relationships of myocardium change during ontogenesis. A negative staircase (a decrease in the isometric force with increasing stimulation rate) in the chick embryo myocardium and a positive steady-state relationship in hatched stage myocardium were revealed. Changes in the force after switching from one stimulation frequency to another, the effects of poststimulation potentiation, as well as responses to the introduction of pauses and extrasystols at a constant stimulation rate were recorded. All the effects observed in the transient processes in preparations from hatched stage myocardium were more pronounced than in embryo myocardium. Our previous mathematical model of calcium recirculation in cardiomyocytes was adapted for simulating the main features of force-interval relationships in embryonal and relatively developed myocardium. The main source of regulatory calcium in the model of hatched stage myocardium is sarcoplasmic reticulum. In the model of embryo myocardium, it was postulated, based on data available in literature, that the main regulator of contractile response of the muscle is calcium that enters cardiomyocytes from extracellular medium. To describe force-interval relationships, by this model, the decreasing dependence of the entry of extracellular calcium on the intervals between stimuli was introduced.
研究了鸡胚和雏鸡心肌制剂的力-间隔关系。结果表明，心肌的力-间隔关系在个体发育过程中会发生变化。在鸡胚心肌中发现了负阶梯现象（等长力随刺激频率增加而降低），在雏鸡阶段心肌中发现了正稳态关系。记录了从一种刺激频率切换到另一种刺激频率后力的变化、刺激后增强效应，以及在恒定刺激频率下引入暂停和期外收缩的反应。在雏鸡阶段心肌制剂的瞬态过程中观察到的所有效应都比胚胎心肌中的更明显。我们之前关于心肌细胞钙再循环的数学模型被用于模拟胚胎和相对发育成熟心肌中力-间隔关系的主要特征。雏鸡阶段心肌模型中调节钙的主要来源是肌浆网。在胚胎心肌模型中，根据文献中的数据推测，肌肉收缩反应的主要调节因子是从细胞外介质进入心肌细胞的钙。通过该模型描述力-间隔关系时，引入了细胞外钙进入对刺激间隔的递减依赖性。
