正常与部分除极的心脏浦肯野纤维膜钠泵活动的比较

SODIUM-PUMP ACTIVITY IN PARTLY DEPOLARIZED CARDIAC PURKINJE'S FIBRES

本研究采用羊心脏浦肯野纤维标本,按其静息膜电位水平分为两组:;≥-75mV的为正常组,-40～-55mV为部分除极组。在降低细胞内外Na^+跨膜梯度的情况下,用细胞内离子选择电极监测细胞内Na^+主动逐出速率以测量细胞膜钠泵活动。结果表明,除极组细胞内Na^+活度(a^1Na)对照值及在预先提高细胞内Na^+水平的情况下所测得的Na^+逐出速半与正常组无显著差别。因而认为,自然部分除极的浦肯野纤维膜钠泵机能并无不可逆转的损伤。其除极原因可能主要与膜对K^+的通透性降低有关。

Cardiac Purkinje's fibres of sheeps were divided into two groups according to their resting potentials: those ≥-75mV as normal group, -40 to - 55mV as partly depolarized group. Under condition of decreased transmembrane Na+gradient, intracellular Na+extrusion was monitored by sodium ion-selective electrodes to assess sodium pump activities. It was suggested from the results that the control values of intracellular sodium activities and the Na+extrusion rates after increase in the level of intracellular sodium exhibited no significant difference between the two groups. It is, therefore, considered that sodium pump function of partly depolarized fibres was not hurt irreversibly and the primary cause responsible for the spontaneous depolarization of some Purkinje's fibres may be the diminution of membrane permeability to potassium.