- 作者: Char-Chang Shieh; Marcy F. Petrini; Terry M. Dwyer; Jerry M. Farley
- 作者服務機構: Departments of; a Pharmacology and Toxicology; b Medicine, and; c Physiology and Biophysics, University of; Mississippi Medical Center, Jackson, Miss., USA
- 中文摘要: --
- 英文摘要: The roles of Ca2+ mobilization in development of tension induced by acetyl- choline (ACh, 0.1 - 100μM) in swine tracheal smooth muscle strips were stud- ied. Under control conditions, ACh induced a transient increase in free cyto- solic calcium concentration ([Ca2+]i) that declined to a steady-state level. The peak increase in [Ca2+]i correlated with the magnitude of tension at each [ACh] after a single exposure to ACh, while the steady-state [Ca2+]i did not. Removal of extracellular Ca2+ had little effect on peak [Ca2+]i but greatly reduced steady-state increases in [Ca2+]i and tension. Verapamil inhibited steady-state [Ca2+]i only at [ACh]<1μM. After depletion of internal Ca2+ stores by 10 min exposure to ACh in Ca2+-free solution and then washout of ACh for 5 min in Ca2+-free solution, simultaneous re-exposure to ACh in the presence of 2.5 mM Ca2+ increased [Ca2+]i to the control steady-state level without over- shoot. The tension attained was the same as control for each [ACh] used. Con- tinuous exposure to successively increasing [ACh] (0.1- 100 μM) also reduced the overshoot of [Ca2+]i at 10 and 100μM ACh, yet tension reached control levels at each [ACh] used. We conclude that the steady-state increase in [Ca2+]i is necessary for tension maintenance and is dependent on Ca2+ influx through voltage-gated calcium channels at 0.1 μM ACh and through a verapamil- insensitive pathway at 10 and 100 μM. The initial transient increase in cal- cium arises from intracellular stores and is correlated with the magnitude of tension only in muscles that have completely recovered from previous expo- sure to agonists.
- 中文關鍵字: --
- 英文關鍵字: Cytosolic Ca2+; Ca2+ sources; Smooth muscle contraction; Tracheal smooth muscle (swine); Acetylcholine