Bretschneider F, Klapperstück M, Löhn M, Markwardt F
Martin-Luther-University Halle-Wittenberg, Julius-Bernstein-Institute for Physiology, Halle/S., Germany.
Pflugers Arch. 1995 Mar;429(5):691-8. doi: 10.1007/BF00373990.
Adenosine 5'-triphosphate-(ATP)-induced whole-cell currents were studied in human B-lymphocytes, transformed by the Epstein-Barr virus, by means of the tight-seal voltage-clamp technique. During bath application of ATP, the membrane conductance was increased. The change of membrane conductance occurred within milliseconds. The dose response relationship for the ATP(4-)-elicited membrane current (Ip) was fitted by the Hill function with a Hill coefficient of 1 and a KD value of 0.2 mmol/l. Adenosine, as well as the Mg(2+)-bound form of ATP, did not effect the membrane conductance. Ip did not desensitize within 1 min and could be evoked repeatedly up to 100 times in 1 cell in the presence of the G-protein blocker Guanosine 5'-o-(2-thiodiphosphate) (GDP [beta S]). Therefore, it seems that ion channels in form of P2Z-purinoceptors are involved in the observed effects. The permeability (P) sequence for cations carrying Ip was PCa:PK:PCs:PNa:PTRIS = 35:2:1.2:1:0.1. The reversal potential of IP was not changed by substitution of intracellular Cl- for aspartate, indicating that anions are not involved in the purinoceptor-dependent conductance. A single-channel conductance of P2Z-receptor-dependent ion channels of about 3 pS was determined by noise analysis of Ip.
利用紧密封接电压钳技术，对经爱泼斯坦-巴尔病毒转化的人B淋巴细胞中5'-三磷酸腺苷（ATP）诱导的全细胞电流进行了研究。在浴槽中施加ATP期间，膜电导增加。膜电导的变化在数毫秒内发生。ATP（4-）诱发的膜电流（Ip）的剂量反应关系用希尔函数拟合，希尔系数为1，KD值为0.2 mmol/l。腺苷以及ATP的镁结合形式均不影响膜电导。在存在G蛋白阻滞剂5'-O-（2-硫代二磷酸）鸟苷（GDP[βS]）的情况下，Ip在1分钟内不会脱敏，并且在1个细胞中可重复诱发多达100次。因此，似乎P2Z嘌呤受体形式的离子通道参与了观察到的效应。携带Ip的阳离子的通透性（P）顺序为PCa:PK:PCs:PNa:PTRIS = 35:2:1.2:1:0.1。用天冬氨酸替代细胞内Cl-不会改变Ip的反转电位，这表明阴离子不参与嘌呤受体依赖性电导。通过对Ip的噪声分析确定了P2Z受体依赖性离子通道的单通道电导约为3 pS。
