Schultheiss G, Hennig B, Diener M
Institute for Veterinary Physiology, Justus-Liebig-University Giessen, Giessen, Germany.
Br J Pharmacol. 2008 Jul;154(5):991-1000. doi: 10.1038/bjp.2008.162. Epub 2008 Apr 21.
The aim of this study was the identification of the mechanism of oxidant-induced intestinal secretion.
The action of H2O2 on ion transport across rat distal colon was evaluated in Ussing chambers. Changes in cytosolic Ca2+ concentration were measured using fura-2.
H2O2 concentration-dependently induced an increase in short-circuit current (Isc), which was due to a stimulation of Cl(-) secretion. The effect of H2O2 was dependent on the presence of serosal Ca2+. It was inhibited after emptying of intracellular Ca2+ stores by cyclopiazonic acid or blockade of ryanodine receptors by ruthenium red, whereas a blocker of inositol 1,4,5-trisphosphate receptors was less effective. Fura 2-experiments confirmed an increase in the cytosolic Ca2+ concentration in the presence of H2O2. Measurements of Cl- currents across the apical membrane at basolaterally depolarized epithelia revealed the activation of a glibenclamide-sensitive, SITS-resistant Cl- conductance by the oxidant. The activation of this conductance was inhibited after blockade of protein kinases with staurosporine. When the apical membrane was permeabilized with nystatin, two sites of action of H2O2 were identified at the basolateral membrane. The oxidant stimulated a basolateral tetrapentylammonium-sensitive K+ conductance and increased the current generated by the Na+-K+ pump. Pretreatment of the tissues with H2O2 reduced the action of subsequently administered Ca2+-, cAMP- and cGMP-dependent secretagogues demonstrating a long-term downregulation after the initial secretory response evoked by the oxidant.
H2O2 affects colonic anion secretion by action sites at both the apical, as well as the basolateral membrane.
本研究旨在确定氧化剂诱导肠道分泌的机制。
在尤斯灌流小室中评估过氧化氢对大鼠远端结肠离子转运的作用。使用fura-2测量胞质Ca2+浓度的变化。
过氧化氢浓度依赖性地诱导短路电流（Isc）增加，这是由于刺激了Cl(-)分泌。过氧化氢的作用依赖于浆膜Ca2+的存在。用环匹阿尼酸排空细胞内Ca2+储存或用钌红阻断ryanodine受体后，其作用受到抑制，而肌醇1,4,5-三磷酸受体阻滞剂的效果较差。Fura 2实验证实，在过氧化氢存在下胞质Ca2+浓度增加。在基底外侧去极化上皮细胞顶膜上测量Cl-电流，结果显示氧化剂激活了一种对格列本脲敏感、对SITS耐药的Cl-电导。用星形孢菌素阻断蛋白激酶后，这种电导的激活受到抑制。当用制霉菌素使顶膜通透时，在基底外侧膜上确定了过氧化氢的两个作用位点。氧化剂刺激了基底外侧对四戊铵敏感的K+电导，并增加了Na+-K+泵产生的电流。用过氧化氢预处理组织可降低随后给予的Ca2+、cAMP和cGMP依赖性促分泌剂的作用，表明在氧化剂引起的初始分泌反应后存在长期下调。
过氧化氢通过顶膜和基底外侧膜上的作用位点影响结肠阴离子分泌。
