Urinary acidification by the turtle bladder is due to a H+-ATPase that is located in the luminal membrane. The rate of H+ transport is stimulated by an increase in the ambient CO2. Using the fluorescent dye acridine orange, we showed that the mitochondria-rich cell of this equilibrium contains vesicles whose internal pH is acidic. We measured the pH of these vesicles by using endocytosed fluorescein isothiocyanate-labeled dextran and found it to be near 5.0. The pH increased after treatment with protonophores or metabolic inhibitors, suggesting that it was due to a H+ pump rather than to a Donnan effect. In bladders preloaded with fluorescent dextran, CO2 stimulated exocytosis and H+ transport measured simultaneously in the same bladder. The increase in the H+ current correlated well with the extent of exocytosis, and both were inhibited by pretreatment with colchicine. We conclude that the turtle bladder contains an intracellular reserve of vesicles containing H+ pumps and CO2 stimulates rapid fusion of these vesicles with the luminal membrane with consequent insertion of H+ pumps, thereby stimulating H+ secretion across the whole epithelium.
展开▼
机译：龟膀胱造成的尿液酸化是由于位于腔膜上的H + -ATPase引起的。 H +的传输速率受周围CO2浓度增加的刺激。使用荧光染料a啶橙，我们表明这种平衡的线粒体富集细胞包含内部酸性为酸性的囊泡。我们使用内吞荧光异硫氰酸荧光素标记的葡聚糖测量了这些囊泡的pH，发现其接近5.0。用质子载体或代谢抑制剂处理后，pH升高，表明这是由于H +泵而不是Donnan效应引起的。在预先装有荧光葡聚糖的膀胱中，在同一膀胱中同时测量了CO2刺激的胞吐作用和H +转运。 H +电流的增加与胞吐程度密切相关，并且都被秋水仙碱预处理抑制。我们得出的结论是，乌龟膀胱包含含有H +泵的囊泡的细胞内储备，而CO2刺激这些囊泡与腔膜快速融合，随后插入H +泵，从而刺激整个上皮细胞的H +分泌。
展开▼
