[摘要]：Background: The tightness of various membrane barriers to CO2 is of unknown molecular origin. Results: The bladder tissue lacks carbonic anhydrase. The resulting low intra-epithelial CO2 concentration gives rise to the apparent CO2 impermeability. Conclusion: Uroplakins do not act to decrease transepithelial CO2 flux. Significance: Enzymatic regulation of CO2 abundance rules out that aquaporins significantly contribute to the maintenance of acid base homeostasis.
