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美国卫生研究院文献>The Journal of Physiology
>CO2 permeability and bicarbonate transport in microperfused interlobular ducts isolated from guinea-pig pancreas
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CO2 permeability and bicarbonate transport in microperfused interlobular ducts isolated from guinea-pig pancreas
class="enumerated" style="list-style-type:decimal">Permeabilities of the luminal and basolateral membranes of pancreatic duct cells to CO2 and HCO3− were examined in interlobular duct segments isolated from guinea-pig pancreas. Intracellular pH (pHi) was measured by microfluorometry in unstimulated, microperfused ducts loaded with the pH-sensitive fluoroprobe 2′7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF).When HCO3−/CO2 was admitted to the bath, pHi decreased transiently as a result of CO2 diffusion and then increased to a higher value as a result of HCO3− uptake across the basolateral membrane by Na+-HCO3− cotransport.When HCO3−/CO2 was admitted to the lumen, pHi again decreased but no subsequent increase was observed, indicating that the luminal membrane was permeable to CO2 but did not allow HCO3− entry to the cells from the lumen. Only when the luminal HCO3− concentration was raised above 125 mm was HCO3− entry detected. The same was true of duct cells stimulated with forskolin.Recovery of pHi from an acid load, induced by exposure to an NH4+ pulse, was dependent on basolateral but not luminal Na+ and could be blocked by basolateral application of methylisobutylamiloride and H2DIDS. This indicates that the Na+-H+ exchangers and Na+-HCO3− cotransporters are located exclusively at the basolateral membrane.In the presence of HCO3−/CO2, substitution of basolateral Cl− with glucuronate caused larger increases in pHi than substitution of luminal Cl−. This suggests that the anion exchanger activity in the basolateral membrane is greater than that in the luminal membrane.We conclude that the luminal and basolateral membranes are both freely permeable to CO2, but while the basolateral membrane has both uptake and efflux pathways for HCO3−, the luminal membrane presents a significant barrier to the re-entry of secreted HCO3−, largely through the inhibition of the luminal anion exchanger by high luminal HCO3− concentrations.
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机译:分离的核酸(多核苷酸),反义寡核苷酸,抑制或减少编码CO2SEN蛋白的消息和/或CO2SEN蛋白或植物多聚核苷酸和多肽多糖的植物植株的表达的方法植物保护细胞,植物细胞,植物片,植物组织或植物,植物的一部分的碳吸收量和碳排量的负,正调节及增加,碳保护层和水流以及CO 2 / CO 2交换水交换或损失水开放植物,关闭植物的气孔,部分植物,器官,植物片或植物细胞,以增强或优化植物,植物片,器官,植物,植物的一部分上的生物量积累,植物,种子或植物细胞中的植物细胞或种子,板温度的降低和蒸腾强度的提高,降低了T型保护细胞中的效率降低和碳含量