Dunne M J, Yule D I, Gallacher D V, Petersen O H
MRC Secretory Control Research Group, Physiological Laboratory, University of Liverpool, England.
J Membr Biol. 1990 Mar;114(1):53-60. doi: 10.1007/BF01869384.
Patch-clamp and single cell [Ca2+]i measurements have been used to investigate the effects of the potassium channel modulators cromakalim, diazoxide and tolbutamide on the insulin-secreting cell line RINm5F. In intact cells, with an average cellular transmembrane potential of -62 +/- 2 mV (n = 42) and an average basal [Ca2+]i of 102 +/- 6 nM (n = 37), glucose (2.5-10 mM): (i) depolarized the membrane, through a decrease in the outward KATP current, (ii) evoked Ca2+ spike potentials, and (iii) caused a sharp rise in [Ca2+]i. In the continued presence of glucose both cromakalim (100-200 microM) and diazoxide (100 microM) repolarized the membrane, terminated Ca2+ spike potentials and attenuated the secretagogue-induced rise in [Ca2+]i. In whole cells (voltage-clamp records) and excised outside-out membrane patches, both cromakalim and diazoxide enhanced the current by opening ATP-sensitive K+ channels. Diazoxide was consistently found to be more potent than cromakalim. Tolbutamide, a specific inhibitor of ATP-sensitive K+ channels, reversed the effects of cromakalim on membrane potential and KATP currents.
膜片钳和单细胞[Ca2+]i测量已被用于研究钾通道调节剂克罗卡林、二氮嗪和甲苯磺丁脲对胰岛素分泌细胞系RINm5F的影响。在完整细胞中，平均细胞跨膜电位为-62±2 mV（n = 42），平均基础[Ca2+]i为102±6 nM（n = 37），葡萄糖（2.5 - 10 mM）：（i）通过降低外向KATP电流使膜去极化，（ii）诱发Ca2+尖峰电位，（iii）导致[Ca2+]i急剧升高。在持续存在葡萄糖的情况下，克罗卡林（100 - 200 μM）和二氮嗪（100 μM）均使膜复极化，终止Ca2+尖峰电位，并减弱促分泌剂诱导的[Ca2+]i升高。在全细胞（电压钳记录）和切除的外向膜片上，克罗卡林和二氮嗪均通过打开ATP敏感性钾通道增强电流。始终发现二氮嗪比克罗卡林更有效。甲苯磺丁脲，一种ATP敏感性钾通道的特异性抑制剂，可逆转克罗卡林对膜电位和KATP电流的影响。
