- 作者: P. Abete; M. Vassalle
- 作者服務機構: Department of Physiology, State University of New York, Health Science Center, Brooklyn, N.Y.,USA
- 中文摘要: --
- 英文摘要: The role of intracellular sodium activity (ai Na) in the control of force was studied in sheep cardiac Purkinje fibers exposed to norepinephrine (NE) and high [Ca]o in the absence and presence of overdrive or of a low concentration of stro- phanthidin. Both NE and high [Ca]o decrease aiNa and increase force, while over- drive increases and low strophanthidin decreases both parameters. In the pres- ence of NE, overdrive increases aiNa less than force and is followed by a more pronounced undershoot in aiNa and force. In contrast, in high [Ca]o overdrive increases aiNa more than force and is followed by a less pronounced undershoot in aiNa and force than in NE. High [Ca]o increases force to a peak, but then the decreasing aiNa reduces force. In all these conditions, aiNa determines force changes during recovery from overdrive. NE and high [Ca]o decrease aiNa less and increase force more in low strophanthidin. Thus, changes in aiNa modulate the increase in force due to increased Ca influx and control force development when Ca influx is either unchanged (low strophanthidin) or has reached a steady state (high [Ca]o, recovery from overdrive).
- 中文關鍵字: --
- 英文關鍵字: Norepinephrine; High [Ca] ; Strophanthidin ; Na/K pump ; Na/Ca exchange