Miyamae S I, Goto K
Department of Physiology, Kanazawa Medical University, Japan.
J Pharmacol Exp Ther. 1988 May;245(2):706-17.
The effect of ethylene glycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) was studied in rabbit sinoatrial node cells treated with ouabain. When isolated sinoatrial node preparations were bathed in the presence of 10(-5) M ouabain in order to depress electrogenic Na-K pump activity, action potentials ceased rapidly. Thereafter, spontaneous miniature fluctuations of less than 2 mV were observed at the resting potential level, while the membrane potential reached a value of about -31 mV. After exposure to the Ca-free 2 mM EGTA solutions, the miniature fluctuations decreased in frequency as well as in amplitude. However, successive exposure to the Ca-free EGTA solutions produced a short series of slow regenerative potentials. Peak amplitude of the slow regenerative potential increased from reduced miniature fluctuations to a maximum value of 46 +/- 3 mV (mean +/- S.E.; n = 10). Resting potential before initiation of the slow regenerative potential reached a value of about -34 mV. Also, Ca-free perfusion produced a small regenerative potential reaching 19 +/- 2 mV (n = 3). In Ca-free EGTA solution, reduction of external Na produced a decrease in amplitude of the slow regenerative potential when choline chloride or LiCl replaced NaCl. Replacement of 25% of the external Na with choline suppressed the slow regenerative potential. Replacement of 60% of the external Na with Li did not affect the slow regenerative potential. Further reduction of the external Na to 0% of the control condition produced a small regenerative potential. Replacement of Na with Li did not abolish the regenerative potential. In the presence of 4 x 10(-6) M verapamil Ca-free EGTA perfusion did not induce a slow regenerative potential. In the presence of 0.7 x 10(-6) M nifedipine Ca-free EGTA perfusion induced a small regenerative potential reaching 27 +/- 5 (n = 3). For low external pH (6.3) obtained with 5% CO2, the slow regenerative potential induced by Ca-free, EGTA perfusion was suppressed, and the regenerative potential amplitude decreased by about 16 mV. Application of 2.5 mM SrCl2 caused a decrease in slow regenerative potential, and the potential decreased by about 21 mV. The slow regenerative potential is not altered noticeably by 10(-5) M tetrodotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)
研究了乙二醇双（β-氨基乙醚）-N，N'-四乙酸（EGTA）对哇巴因处理的兔窦房结细胞的影响。当分离的窦房结标本在10⁻⁵ M哇巴因存在下浸泡以抑制生电钠钾泵活性时，动作电位迅速停止。此后，在静息电位水平观察到小于2 mV的自发微小波动，而膜电位达到约-31 mV的值。暴露于无钙的2 mM EGTA溶液后，微小波动的频率和幅度均降低。然而，连续暴露于无钙的EGTA溶液会产生一系列短暂的缓慢再生电位。缓慢再生电位的峰值幅度从降低的微小波动增加到最大值46±3 mV（平均值±标准误；n = 10）。缓慢再生电位开始前的静息电位达到约-34 mV的值。此外，无钙灌注产生一个小的再生电位，达到19±2 mV（n = 3）。在无钙EGTA溶液中，当用氯化胆碱或氯化锂替代氯化钠时，降低细胞外钠会导致缓慢再生电位的幅度降低。用胆碱替代25%的细胞外钠会抑制缓慢再生电位。用锂替代60%的细胞外钠不影响缓慢再生电位。将细胞外钠进一步降低至对照条件的0%会产生一个小的再生电位。用锂替代钠不会消除再生电位。在4×10⁻⁶ M维拉帕米存在下，无钙EGTA灌注不会诱导缓慢再生电位。在0.7×10⁻⁶ M硝苯地平存在下，无钙EGTA灌注诱导一个小的再生电位，达到27±5（n = 3）。对于用5%二氧化碳获得的低细胞外pH（6.3），无钙EGTA灌注诱导的缓慢再生电位受到抑制，再生电位幅度降低约16 mV。应用2.5 mM氯化锶会导致缓慢再生电位降低，电位降低约21 mV。10⁻⁵ M河豚毒素对缓慢再生电位没有明显影响。（摘要截断于400字）
