Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.
Laboratory of Drug Disposition and Pharmacokinetics, Faculty of Pharma-Sciences, Teikyo University, Kaga 2-11-1, Tokyo 173-8605, Japan.
Int J Mol Sci. 2023 May 19;24(10):9003. doi: 10.3390/ijms24109003.
Putrescine is a bioactive polyamine. Its retinal concentration is strictly controlled to maintain a healthy sense of vision. The present study investigated putrescine transport at the blood-retinal barrier (BRB) to gain a better understanding of the mechanisms of putrescine regulation in the retina. Our microdialysis study showed that the elimination rate constant during the terminal phase was significantly greater (1.90-fold) than that of [C]D-mannitol, which is a bulk flow marker. The difference in the apparent elimination rate constants of [H]putrescine and [C]D-mannitol was significantly decreased by unlabeled putrescine and spermine, suggesting active putrescine transport from the retina to the blood across the BRB. Our study using model cell lines of the inner and outer BRB showed that [H]putrescine transport was time-, temperature-, and concentration-dependent, suggesting the involvement of carrier-mediated processes in putrescine transport at the inner and outer BRB. [H]Putrescine transport was significantly reduced under Na-free, Cl-free, and K-replacement conditions, and attenuated by polyamines or organic cations such as choline, a choline transporter-like protein (CTL) substrate. Rat CTL1 cRNA-injected oocytes exhibited marked alterations in [H]putrescine uptake, and CTL1 knockdown significantly reduced [H]putrescine uptake in model cell lines, suggesting the possible participation of CTL1 in putrescine transport at the BRB.
腐胺是一种生物活性多胺。其视网膜浓度受到严格控制，以维持健康的视觉。本研究调查了血液视网膜屏障 (BRB) 中的腐胺转运，以更好地了解腐胺在视网膜中的调节机制。我们的微透析研究表明，终相的消除速率常数明显大于（1.90 倍）作为大分子量示踪剂的[C]D-甘露醇。[H]腐胺和[C]D-甘露醇的表观消除速率常数的差异，通过未标记的腐胺和精胺显著降低，表明腐胺从视网膜向血液跨 BRB 的主动转运。我们使用内 BRB 和外 BRB 的模型细胞系进行的研究表明，[H]腐胺的转运是时间、温度和浓度依赖性的，表明载体介导的过程参与了内 BRB 和外 BRB 中的腐胺转运。在无 Na、无 Cl 和 K 替代条件下，[H]腐胺转运显著减少，并被多胺或有机阳离子如胆碱（一种胆碱转运蛋白样蛋白 [CTL] 底物）减弱。大鼠 CTL1 cRNA 注射卵母细胞表现出 [H]腐胺摄取的明显改变，CTL1 敲低显著降低了模型细胞系中的 [H]腐胺摄取，表明 CTL1 可能参与了 BRB 中的腐胺转运。
