Belloni F L, Elkin P L, Giannotto B
Br J Pharmacol. 1985 Jun;85(2):441-6. doi: 10.1111/j.1476-5381.1985.tb08880.x.
Uptake of [14C]-adenosine into freshly dispersed rat hepatocytes was inhibited 44% by dipyridamole (50 microM) and 60% by nitrobenzylthioinosine (NBTI, 20 microM). The results are consistent with the known ability of these drugs to inhibit adenosine transport in other cell types. The nucleotide analogue, alpha, beta-methylene adenosine diphosphate (AOPCP, 50 microM), inhibited by 84% the degradation of exogenous 5' AMP that occurred rapidly when this substrate alone was presented to isolated hepatocytes. This confirms the ecto-5'-nucleotidase inhibitory properties of this analogue in isolated hepatocytes. During hypoxic incubation, isolated hepatocytes released adenosine, which accumulated in the extracellular volume. Dipyridamole and NBTI each markedly attenuated this extracellular adenosine accumulation. In contrast, AOPCP had no inhibitory effect on net hypoxic adenosine release. It is concluded that hypoxic rat hepatocytes produce adenosine intracellularly and that this adenosine is released via facilitated diffusion to the extracellular space, based on the inhibition observed with the transport inhibitors. The plasma membrane enzyme ecto-5'-nucleotidase does not appear to participate in hypoxic adenosine release from these cells as indicated by the lack of effect of the nucleotidase inhibitor, AOPCP.
双嘧达莫（50微摩尔）使[14C] - 腺苷进入新鲜分离的大鼠肝细胞的摄取量降低了44%，而硝基苄硫基肌苷（NBTI，20微摩尔）则使其降低了60%。这些结果与这些药物在其他细胞类型中抑制腺苷转运的已知能力一致。核苷酸类似物α，β - 亚甲基腺苷二磷酸（AOPCP，50微摩尔），当单独将该底物提供给分离的肝细胞时，能迅速发生的外源性5' - AMP降解受到84%的抑制。这证实了该类似物在分离的肝细胞中具有抑制胞外5' - 核苷酸酶的特性。在缺氧孵育期间，分离的肝细胞释放腺苷，腺苷在细胞外液中积累。双嘧达莫和NBTI均显著减弱了这种细胞外腺苷的积累。相比之下，AOPCP对缺氧腺苷的净释放没有抑制作用。基于转运抑制剂所观察到的抑制作用，得出的结论是，缺氧的大鼠肝细胞在细胞内产生腺苷，并且这种腺苷通过易化扩散释放到细胞外空间。如核苷酸酶抑制剂AOPCP缺乏作用所表明的，质膜酶胞外5' - 核苷酸酶似乎不参与这些细胞缺氧时腺苷的释放。
