Saldeña T A, Sasso A J, Cincunegui Liliana M, Carra Graciela E, Codina María Victoria, Saraví F D
Departamento de Morfofisiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina.
Acta Gastroenterol Latinoam. 2003;33(3):119-27.
Rat distal colon epithelium is frequently employed to assess the effect of natural and synthetic chemicals on chloride secretion. Inhibition of chloride secretion is often reported as the loop diuretic-sensitive portion of short-circuit current (Isc). The present work challenges the hypothesis that a loop diuretic alone is able to fully abolish chloride secretion. Isolated mucosa preparations were mounted in an Ussing chamber. The effects on short-circuit current of replacement of normal Ringer by a low (2.5 mmol/L) Cl solution and of blockers of basolateral Na, K, 2 Cl symport (bumetanide), apical Cl channels (diphenylamine-2-carboxylate, DPC), and anion exchange (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid, SITS) alone and combined were assessed. Low Cl reversibly decreased Isc by 76%. In normal Ringer, bumetanide decreased Isc by 65%. SITS also had a significant effect at the serosal side, but not at the apical side, where DPC caused a 40% decrease. Chloride replacement, bumetanide and DPC, but not SITS, increased epithelial resistivity. Combined blockade of Na, K, 2 Cl symport and apical Cl channels, of Na, K, 2 Cl symport and anion antiport, or of anion antiport and apical Cl channels was needed to achieve reduction of short circuit current to the same extent seen with chloride replacement. Present results indicate that Isc of the unstimulated epithelium is mostly due to chloride secretion, and at least two blockers are required to abolish it. This fact should be taken into account in studies of chloride secretion-stimulating agents.
大鼠远端结肠上皮经常被用于评估天然和合成化学物质对氯离子分泌的影响。氯离子分泌的抑制通常被报告为短路电流（Isc）中对袢利尿剂敏感的部分。目前的研究对仅用一种袢利尿剂就能完全消除氯离子分泌的假说提出了质疑。将分离的黏膜制剂安装在尤斯灌流小室中。评估了用低氯（2.5 mmol/L）溶液替代正常林格液以及单独和联合使用基底外侧钠钾氯同向转运体阻滞剂（布美他尼）、顶端氯通道阻滞剂（二苯胺-2-羧酸盐，DPC）和阴离子交换阻滞剂（4-乙酰氨基-4'-异硫氰酸基芪-2,2'-二磺酸，SITS）对短路电流的影响。低氯使Isc可逆性降低76%。在正常林格液中，布美他尼使Isc降低65%。SITS在浆膜侧也有显著作用，但在顶端侧没有，DPC在顶端侧使Isc降低40%。氯离子替代、布美他尼和DPC，但不是SITS，增加了上皮电阻。需要联合阻断钠钾氯同向转运体和顶端氯通道、钠钾氯同向转运体和阴离子反向转运体或阴离子反向转运体和顶端氯通道，才能使短路电流降低到与氯离子替代相同的程度。目前的结果表明，未受刺激的上皮的Isc主要归因于氯离子分泌，并且至少需要两种阻滞剂才能消除它。在研究刺激氯离子分泌的药物时应考虑这一事实。
