Mølstad P
Biochim Biophys Acta. 1980 Mar 27;597(1):166-73. doi: 10.1016/0005-2736(80)90160-1.
The efflux of L-[3H]carnitine was studied in cells from an established cell line from human heart (Girardi human heart cells, CCL 27). The cells were loaded with 4 mumol/l L-[3H]carnitine for 1 or 24 h, and the efflux of radioactivity into the medium was measured. The amount of intracellular L-[3H]-carnitine retained was expressed as a function of time. The results were fitted to an exponential equation, from which efflux rate constants were computed. Increasing the extracellular concentration of butyrobetaine, L-carnitine, D-carnitine, betaine, DL-norcarnitine or 3-dimethylamino-2-hydroxypropionic acid each increased the observed efflux. This is most likely due to accelerated exchange diffusion. The substrate specificity of this accelerated exchange diffusion is different from what previously has been found in competitive uptake studies of L-carnitine. L-Carnitine was preferentially released to L-acetylcarnitine, and blocking the sulfhydryl groups with 5,5-dithiobis-(2-nitrobenzoic acid) increased the efflux.
在源自人心脏的一个已建细胞系（吉拉尔迪人心肌细胞，CCL 27）的细胞中研究了L-[3H]肉碱的流出。细胞用4 μmol/L的L-[3H]肉碱加载1或24小时，然后测量放射性物质向培养基中的流出。保留的细胞内L-[3H]肉碱量表示为时间的函数。将结果拟合到一个指数方程，由此计算流出速率常数。增加丁酸甜菜碱、L-肉碱、D-肉碱、甜菜碱、DL-去甲肉碱或3-二甲基氨基-2-羟基丙酸的细胞外浓度均增加了观察到的流出。这很可能是由于加速的交换扩散。这种加速交换扩散的底物特异性与先前在L-肉碱的竞争性摄取研究中发现的不同。L-肉碱优先释放为L-乙酰肉碱，用5,5-二硫代双-(2-硝基苯甲酸)封闭巯基会增加流出。
