The intracellular pH (pHi) of large nerve cells from the mollusc, Helix aspersa, was measured with pH-sensitive micro-electrodes. Cells were held under voltage clamp and the effect on pHi of different holding potentials was determined. 2. Depolarization of the cell from the resting potential (about -50 mV) to -10 mV produced a fall in pHi that could be reduced by bathing the cell in nominally Ca2+-free saline. 3. At positive holding potentials pHi increased to a steady level that depended upon the electrochemical gradient for H+ across the cell membrane; it shifted by about 1 unit when the external pH was increased from 7 to 8 (or when the membrane potential increased by 58 mV, Thomas & Meech, 1982). 4. The depolarization-induced increase in H+ permeability was insensitive to SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid, 20 microM), which blocks pHi regulation at the resting potential in these cells (Thomas, 1976). When pHi was displaced from a steady level by ionophoretic injection of HCl, there was a rapid recovery at depolarized potentials even in the presence of SITS. The H+ pathway appeared to be little affected by prolonged periods at positive membrane potentials. 5. The depolarization-induced H+ efflux was insensitive to the metabolic inhibitor CCmP (carbonyl cyanide-m-chlorophenylhydrazone, 20 microM) and persisted in cells bathed in pH-buffered n-methyl glucamine-gluconate. It was also insensitive to DCCD (N, N'-dicyclohexylcarbodiimide, 10-100 microM) and oligomycin (2-10 micrograms/ml). 6. The H+ pathway could be fully blocked by 1 mM-ZnCl2, 1 mM-LaCl3, 1 mM-CuCl2, 2 mM-CdCl2 or 10 mM-CoCl2. Other divalent ions such as BaCl2 (10 mM) produced a block at membrane potentials near 0 mV but the block was released at more positive potentials. Low levels of LaCl3 (0.1 mM), the organic Ca2+ channel antagonist D600 (100 mg/ml) and high levels of the K+ channel blocker TEA (50 mM) all had similar effects to Ba2+. 7. The K+ channel blocker 4-aminopyridine (10 mM), which blocks H+ currents in perfused Lymnaea neurones (Byerly, Meech & Moody, 1984), has a complex action.(ABSTRACT TRUNCATED AT 400 WORDS)
摘要
用对pH敏感的微电极测量了软体动物皱襞蛞蝓大神经细胞的细胞内pH值（pHi）。细胞在电压钳制下保持，测定了不同钳制电位对pHi的影响。2. 细胞从静息电位（约-50 mV）去极化到-10 mV会导致pHi下降，而将细胞置于名义上无Ca2+的盐溶液中孵育可使其下降幅度减小。3. 在正钳制电位下，pHi会升高至一个稳定水平，该水平取决于H+跨细胞膜的电化学梯度；当外部pH从7增加到8时（或当膜电位增加58 mV时，托马斯和米奇，1982年），pHi会偏移约1个单位。4. 去极化诱导的H+通透性增加对SITS（4-乙酰氨基-4'-异硫氰基芪-2,2'-二磺酸，20 μM）不敏感，SITS会阻断这些细胞在静息电位时的pHi调节（托马斯，1976年）。当通过离子电泳注入HCl使pHi偏离稳定水平时，即使存在SITS，在去极化电位下仍会迅速恢复。长时间处于正膜电位下，H+通道似乎几乎不受影响。5. 去极化诱导的H+外流对代谢抑制剂CCmP（羰基氰化物间氯苯腙，20 μM）不敏感，并且在pH缓冲的N-甲基葡糖胺-葡萄糖酸盐中孵育的细胞中持续存在。它对DCCD（N,N'-二环己基碳二亚胺，10 - 100 μM）和寡霉素（2 - 10 μg/ml）也不敏感。6. H+通道可被1 mM - ZnCl2、1 mM - LaCl3、1 mM - CuCl2、2 mM - CdCl2或10 mM - CoCl2完全阻断。其他二价离子如BaCl2（10 mM）在膜电位接近0 mV时产生阻断，但在更正的电位下阻断解除。低水平的LaCl3（0.1 mM）、有机Ca2+通道拮抗剂D600（100 mg/ml）和高水平的K+通道阻滞剂TEA（50 mM）都与Ba2+有类似作用。7. K+通道阻滞剂4-氨基吡啶（10 mM）可阻断灌注的椎实螺神经元中的H+电流（拜利、米奇和穆迪，1984年），其作用复杂。（摘要截取自400字）
