Thyroid hormone export from cells: contribution of P-glycoprotein
Thyroid hormone export from cells: contribution of P-glycoprotein
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DOI：
10.1677/joe.1.06096
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发表时间：
2005-04-01
影响因子：
4
通讯作者：
Mortimer, RH
中科院分区：
文献类型：
--
作者：
Mitchell, AM;Tom, M;Mortimer, RH
维拉帕米抑制三碘甲腺原氨酸（T-3）从几种细胞类型的流出，表明多药耐药相关（MDR）蛋白参与T-3转运。然而，尚未研究P-糖蛋白（P-gp）的直接参与。我们比较了I-125-T-3在MDCKII细胞（MDCKII-MDR）和野生型MDCKII细胞（MDCKII）中的转运，并研究了常规（维拉帕米和尼群地平）和特异性MDR抑制剂（VX 853和VX 710）对I-125-T-3外排的影响。我们通过Western blotting证实了MDCKII-MDR细胞中P-gp的表达增强。计算的MDCKII-MDR细胞的I-125-T-3外排速率（约0.30/min）比MDCKII细胞（约0.15/min）增加两倍。总体而言，与MDCKII细胞相比，MDCKII-MDR细胞中I-125-T-3的细胞蓄积减少了26%，这可能反映了MDCKII-MDR细胞中T-3的输出增强，而不是细胞摄取减少，因为P-gp通常从细胞中输出物质。维拉帕米使MDCKII和MDCKII-MDR细胞的I-125-T-3外排率分别降低42%和66%，而尼群地平使I-125-T-3外排率分别降低36%和48%，表明这两种物质抑制除P-gp外的其他细胞T-3转运蛋白。特异性MDR抑制剂VX 853和VX 710对野生型MDCK Ⅱ细胞I-125-T-3外排率无影响，但对MDCK Ⅱ-MDR细胞I-125-T-3外排率分别降低50%和53%。这些结果提供了P-gp从细胞输出甲状腺激素的第一个直接证据。
Verapamil inhibits tri-iodothyronine (T-3) efflux from several cell types, suggesting the involvement of multidrug resistance-associated (MDR) proteins in T-3 transport. The direct involvement of P-glycoprotein (P-gp) has not, however, been investigated. We compared the transport of I-125-T-3 in MDCKII cells that had been transfected with mdr1 cDNA (MDCKII-MDR) versus wild-type MDCKII cells (MDCKII), and examined the effect of conventional (verapamil and nitrendipine) and specific MDR inhibitors (VX 853 and VX 710) on I-125-T-3 efflux. We confirmed by Western blotting the enhanced expression of P-gp in MDCKII-MDR cells. The calculated rate of I-125-T-3 efflux from MDCKII-MDR cells (around 0.30/min) was increased twofold compared with MDCKII cells (around 0.15/min). Overall, cellular accumulation of I-125-T-3 was reduced by 26% in MDCKII-MDR cells compared with MDCKII cells, probably reflecting enhanced export of T-3 from MDCKII-MDR cells rather than reduced cellular uptake, as P-gp typically exports substances from cells. Verapamil lowered the rate of I-125-T-3 efflux from both MDCKII and MDCKII-MDR cells by 42% and 66% respectively, while nitrendipine reduced I-125-T-3 efflux rate by 36% and 48% respectively, suggesting that both substances inhibited other cellular T-3 transporters in addition to P-gp. The specific MDR inhibitors VX 853 and VX 710 had no effect of I-125-T-3 efflux rate from wild-type MDCKII cells but reduced I-125-T-3 export in MDCKII-MDR cells by 50% and 53% respectively. These results have provided the first direct evidence that P-gp exports thyroid hormone from cells.