Nucleoside and nucleobase transporters of primary human cardiac microvascular endothelial cells: characterization of a novel nucleobase transporter
Nucleoside and nucleobase transporters of primary human cardiac microvascular endothelial cells: characterization of a novel nucleobase transporter
复制标题
DOI：
10.1152/ajpheart.01006.2007
复制
发表时间：
2007-12-01
影响因子：
4.8
通讯作者：
Hammond, James R.
中科院分区：
文献类型：
--
作者：
Bone, Derek B. J.;Hammond, James R.
心血管活性代谢物（如腺苷）的水平受内皮细胞核苷转运蛋白的调节。我们表征了原代人心脏微血管内皮细胞（hMVECs）的核苷和核碱基转运能力。hMVECs通过硝基苯巯基嘌呤核糖体敏感平衡核苷转运体1 （ENT1）积累2-[H-3]氯腺苷，最大v值为3.4 +/- 1 pmol。μl(1)。s(-1)，没有硝基巯基嘌呤核糖体不敏感的ENT2的贡献。ENT1阻滞剂对2-氯腺苷摄取的抑制产生了单相抑制曲线，这也与最小ENT2表达相容。核碱基[H-3]次黄嘌呤在hMVECs内积累（K-m = 96 +/- 37 μ M; V-max = 1.6 +/- 0.3 pmol）。μl(1)。S(-1))，尽管缺乏已知的核碱基转运系统。这种新型转运体对双嘧达莫不敏感，但可以被腺嘌呤（K-i = 19 +/- 7 μ M）和其他嘌呤核碱基（包括化疗类似物）抑制。多种其他细胞类型也表达核碱基转运蛋白，包括核苷转运蛋白缺陷的PK（15）细胞系（PK15NTD）。PK15NTD细胞中[H-3]次黄嘌呤摄取的进一步表征表明不依赖于Na+或H+。在ENT2抑制剂双嘧达莫存在的情况下，表达人ENT2的PK15NTD细胞积累的[H-3]次黄嘌呤比PK15NTD细胞或hMVECs多4.5倍，表明可捕获ENT2渗透性代谢物。了解核苷和核碱基转运体在脉管系统中的作用，将有助于进一步研究它们在缺氧或缺血等病理生理条件下的作用。
Levels of cardiovascular active metabolites, like adenosine, are regulated by nucleoside transporters of endothelial cells. We characterized the nucleoside and nucleobase transport capabilities of primary human cardiac microvascular endothelial cells (hMVECs). hMVECs accumulated 2-[H-3]chloroadenosine via the nitrobenzylmercaptopurine riboside-sensitive equilibrative nucleoside transporter 1 (ENT1) at a V-max of 3.4 +/- 1 pmol.mu l(-1).s(-1), with no contribution from the nitrobenzylmercaptopurine riboside-insensitive ENT2. Inhibition of 2-chloroadenosine uptake by ENT1 blockers produced monophasic inhibition curves, which are also compatible with minimal ENT2 expression. The nucleobase [H-3]hypoxanthine was accumulated within hMVECs (K-m = 96 +/- 37 mu M; V-max = 1.6 +/- 0.3 pmol.mu l(-1).s(-1)) despite the lack of a known nucleobase transport system. This novel transporter was dipyridamole-insensitive but could be inhibited by adenine (K-i = 19 +/- 7 mu M) and other purine nucleobases, including chemotherapeutic analogs. A variety of other cell types also expressed the nucleobase transporter, including the nucleoside transporter-deficient PK(15) cell line (PK15NTD). Further characterization of [H-3] hypoxanthine uptake in the PK15NTD cells showed no dependence on Na+ or H+. PK15NTD cells expressing human ENT2 accumulated 4.5-fold more [H-3] hypoxanthine in the presence of the ENT2 inhibitor dipyridamole than did PK15NTD cells or hMVECs, suggesting trapping of ENT2-permeable metabolites. Understanding the nucleoside and nucleobase transporter profiles in the vasculature will allow for further study into their roles in pathophysiological conditions such as hypoxia or ischemia.