氨脉冲酸化蟾蜍膀胱膜上皮细胞的研究

Acid Load in Epithelial Cells of Toad Urinary Bladder by Ammonia Prepulse Technique

用pH荧光探剂2,7-二环(2-羧乙基)-5(6)-羧基荧光黄(BCECF)研究氨脉冲对蟾蜍膀胱上皮细胞的酸化效果,测量细胞内pH(pHi)值的变化. 当用25mmol NH4Cl溶液作用于膀胱膜浆液面(S面)时,pHi值负增长0.15,细胞被酸化;而作用于粘液面(M面)时不能酸化细胞. 将50molBa2+加到S面,细胞的酸化被阻止. 这说明+4NH通过上皮细胞底侧膜的K+通道进入细胞使pHi降低. 用季胺离子(TMA+)代替Na+,能加大酸化幅度. 1 mmol amiloride能使pHi回升速度和幅度都大大降低,这表明位于上皮细胞顶膜的Na+/H+交换参与了pHi调节.

To evaluate the possibility of acid load on epithelial cells of toad urinary bladder by ammonia prepulse technique, pH-sensitive dye 2,7-bis(2-carboxyethyl)-5(6)-carboxylfluorescein (BCECF) was used to measure intracellular pH(pHi)of these cells. An acid-load undershoots about 0.15 pH was observed when 25 mmol NH4Cl solution perfused the serosal side, but this phenomenon didn抰 happen when the mucosal side was prefused. 50molBa2+-K+ channel inhibitor was added into the serosal solution can decrease the pHi undershoot almost completely. This suggests that +4NH, which reduces pHi, enter cell via K+ channel located on basolateral membrane. Substituting TMA+ for Na+ enhance acidifying effect. 1 mmol amiloride decreased pHi recovery considerably both in rate and in range. This indicates that the apical Na+/H+ exchange is involved in pHi regulation.