Schultz J E, Schönborn C
Universität Tübingen, Fakultät für Chemie und Pharmazie, Germany.
FEBS Lett. 1994 Dec 19;356(2-3):322-6. doi: 10.1016/0014-5793(94)01300-4.
Responses of the cAMP generating system of Tetrahymena to changes in the concentrations of external [K+] or [Ca2+] ions were examined. When Tetrahymena are equilibrated in high [K+] buffers, intracellular levels of cAMP decreased to 40% within 2 h. Hyperpolarization of the cells by dilution of external [K+] to one-eighth of its original concentration instantly stimulated intracellular cAMP formation. Manipulations of the K+ resting conductance of Tetrahymena by equilibration in buffers of different K+ content greatly affected the responsivity of the adenylyl cyclase. Hyperpolarization of the cell by addition of Ca2+ also resulted in a rapid generation of cAMP. Blockade of K+ conductances by the K+ channel blockers tetraethylammonium, quinine, and Cs+, dose-dependently inhibited hyperpolarization-stimulated cAMP formation. The data indicate that a hyperpolarization-activated K+ current is directly coupled to adenylyl cyclase regulation.
研究了四膜虫中环磷酸腺苷（cAMP）生成系统对外部[K⁺]或[Ca²⁺]离子浓度变化的反应。当四膜虫在高[K⁺]缓冲液中达到平衡时，细胞内cAMP水平在2小时内降至40%。通过将外部[K⁺]稀释至其原始浓度的八分之一使细胞超极化，可立即刺激细胞内cAMP的形成。通过在不同K⁺含量的缓冲液中平衡来操纵四膜虫的K⁺静息电导，极大地影响了腺苷酸环化酶的反应性。添加Ca²⁺使细胞超极化也导致cAMP的快速生成。K⁺通道阻滞剂四乙铵、奎宁和Cs⁺对K⁺电导的阻断，剂量依赖性地抑制超极化刺激的cAMP形成。数据表明，超极化激活的K⁺电流直接与腺苷酸环化酶调节相关联。
