cAMP stimulates fluorescent bile acid uptake into hepatocytes by membrane hyperpolarization.
cAMP stimulates fluorescent bile acid uptake into hepatocytes by membrane hyperpolarization.
复制标题
cAMP 通过膜超极化刺激肝细胞摄取荧光胆汁酸。
DOI：
10.1152/ajpgi.1996.270.2.g339
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Weinman,SA
中科院分区：
文献类型：
--
作者：
Grune,S;Meng,XJ;Weinman,SA
细胞内3‘，5’-环磷酸腺苷(CAMP)升高可使肝细胞超极化，增加胆汁酸摄取率。这项研究的目的是确定这两种现象在多大程度上存在联系。用荧光胆汁酸类似物(FBA)检测胆汁酸向全细胞膜片钳肝细胞的转运。Na(+)依赖性摄取净电荷为-1的胆基-硝基-2-氧杂-1，3-二唑-4-赖氨酸(C-NBD-L)是电摄取，而净电荷为-2的FBA-胆酰甘氨酰胺荧光素(CGAMF)摄取是中性的。8-溴环腺苷(8-BrcAMP；100微米)与肝细胞孵育可使电转运的FBA摄取率增加25%(P=0.002)，但对电中和转运的FBA摄取率无明显影响。微电极穿刺法显示，8-BrcAMP或Forsklin使肝细胞超极化6-8 mV。为了确定超极化是否与cAMP诱导的摄取速率增加有关，在电压钳条件下，在全细胞膜片钳条件下将cAMP直接引入肝细胞。只要电压钳电压维持在-30 mV，就不能刺激C-NBD-L摄取。然而，当电压钳以移走移液管或电流钳终止时，cAMP使摄取率增加25-34%(P<；0.002)。在这两种方案中，cAMP对电子中和转运的FBA CGamF的摄取没有影响。最后，在没有cAMP的电压钳制的肝细胞中，10 mV的超极化使C-NBD-L的摄取率增加了23%。因此，我们得出结论，cAMP短期刺激肝细胞摄取荧光胆汁酸是膜超极化的直接结果。
Elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) hyperpolarizes hepatocytes and increases the uptake rate of bile acids. The purpose of this study was to determine to what extent these two phenomena are linked. Fluorescent bile acid analogues (FBA) were used to probe bile acid transport into whole cell patch-clamped hepatocytes. Na(+)-dependent uptake of cholyl-nitrobenz-2-oxa-1,3-diazol-4-yl-lysine (C-NBD-L), an FBA with a net charge of -1, was shown to be electrogenic, whereas uptake of cholylglycylamidofluorescein (CGamF), an FBA with a net charge of -2, was neutral. Incubation of hepatocytes with 8-bromo-cAMP (8-BrcAMP; 100 microM) increased the uptake rate of the electrogenically transported FBA by 25% (P = 0.002), but had no effect on the uptake rate of the electroneutrally transported FBA. Microelectrode impalements revealed that 8-BrcAMP or forskolin hyperpolarized hepatocytes by 6-8 mV. To determine if hyperpolarization is responsible for the cAMP-induced increase in uptake rate, cAMP was directly introduced into hepatocytes during whole cell patch clamp under voltage-clamp conditions. As long as voltage clamp was maintained at -30 mV there was no stimulation of C-NBD-L uptake. However, when voltage clamp was terminated by either pipette removal or current clamp, cAMP increased the uptake rate by 25-34% (P < 0.002). In both of these protocols, cAMP had no effect on uptake of the electroneutrally transported FBA, CGamF. Finally, in voltage-clamped hepatocytes in the absence of cAMP, a 10-mV hyperpolarization increased the uptake rate of C-NBD-L by 23%. We therefore conclude that short-term cAMP-induced stimulation of fluorescent bile acid uptake in hepatocytes is a direct consequence of membrane hyperpolarization.