Anwer M S, Nolan K, Hardison W G
Department of Veterinary Medicine, Tufts University School of Veterinary Medicine, N. Grafton, Massachusetts 01536.
Am J Physiol. 1988 Dec;255(6 Pt 1):G713-22. doi: 10.1152/ajpgi.1988.255.6.G713.
Hepatic transport of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) was studied in isolated perfused rat livers and in isolated rat hepatocytes to determine if DIDS-induced decrease in biliary HCO3- excretion is due to a DIDS-HCO3- exchange and/or due to inhibition of Cl(-)-HCO3- exchange. In isolated perfused rat livers, DIDS reversibly decreased biliary HCO3- concentration and excretion. The changes in biliary HCO3- concentration were inversely related to biliary DIDS concentration. DIDS was concentrated in bile, indicating active hepatic transport. Replacement of perfusate HCO3- with equimolar dimethyloxazolidinedione (DMO) or tricine decreased biliary excretion, but not hepatic uptake, of DIDS. Biliary excretion of DIDS was also associated with a decrease in bile pH, and this decrease in pH was greater in the presence of HCO3-. HCO3-, but not DMO or tricine, stimulated DIDS efflux from preloaded hepatocytes. DIDS efflux was also temperature dependent and increased with increasing extracellular pH. Collectively, these results are consistent with the presence of a DIDS-HCO3- (OH-) exchange mechanism at the canalicular membrane. HCO3(-)-dependent Cl- uptake in hepatocytes was competitively inhibited by DIDS (Ki = 0.24 mM), confirming the presence of DIDS-inhibitable Cl(-)-HCO3- exchange. However, the ability of DIDS to decrease biliary HCO3- excretion persisted when perfusate Cl- was replaced by isethionate. Moreover, biliary HCO3- concentration returned to base line despite the presence of 2-6 mM DIDS in bile. Thus it seems unlikely that the inhibition of Cl(-)-HCO3- exchange by DIDS is a major mechanism of inhibition of HCO3- excretion. We, therefore, conclude that a DIDS-HCO3- (OH-) exchange at the canalicular membrane is the most likely explanation for the observed decrease in biliary HCO3- excretion.
在离体灌注大鼠肝脏和离体大鼠肝细胞中研究了4,4'-二异硫氰基芪-2,2'-二磺酸（DIDS）的肝脏转运，以确定DIDS诱导的胆汁中HCO3-排泄减少是由于DIDS-HCO3-交换和/或由于抑制Cl(-)-HCO3-交换。在离体灌注大鼠肝脏中，DIDS可逆地降低胆汁中HCO3-浓度和排泄。胆汁中HCO3-浓度的变化与胆汁中DIDS浓度呈负相关。DIDS在胆汁中被浓缩，表明肝脏有主动转运。用等摩尔的二甲基恶唑烷二酮（DMO）或三羟甲基氨基甲烷替代灌注液中的HCO3-可降低DIDS的胆汁排泄，但不影响其肝脏摄取。DIDS的胆汁排泄还与胆汁pH值降低有关，在有HCO3-存在时这种pH值降低更大。HCO3-而非DMO或三羟甲基氨基甲烷刺激预加载的肝细胞中DIDS流出。DIDS流出也依赖温度，并随细胞外pH值升高而增加。总体而言，这些结果与在胆小管膜存在DIDS-HCO3-（OH-）交换机制一致。DIDS竞争性抑制肝细胞中HCO3-依赖性Cl-摄取（Ki = 0.24 mM），证实存在可被DIDS抑制的Cl(-)-HCO3-交换。然而，当灌注液中的Cl-被羟乙基磺酸替代时，DIDS降低胆汁中HCO3-排泄的能力仍然存在。此外，尽管胆汁中存在2-6 mM DIDS，胆汁中HCO3-浓度仍恢复到基线。因此，DIDS抑制Cl(-)-HCO3-交换似乎不太可能是抑制HCO3-排泄的主要机制。因此，我们得出结论，胆小管膜处的DIDS-HCO3-（OH-）交换最有可能解释观察到的胆汁中HCO3-排泄减少。
