Department of Pharmacology and Therapeutics, University of Manitoba, A220-753 McDermot Avenue, Winnipeg, MB R3E 0T6, Canada.
Can J Physiol Pharmacol. 2009 Oct;87(10):821-30. doi: 10.1139/Y09-072.
Previous studies showed that amantadine transport increased while tetraethylammonium (TEA) transport decreased in kidney tissue from diabetic rats. Changes in transport activity were reversed by exogenous insulin. We hypothesized that this difference in transport regulation is due to differential regulation of different transport systems. Native human embryonic kidney cortex cells (HEK293 cell line) and rat organic cation transporter (rOCT)-transfected cells were used to test the hypothesis. In support of differential regulation, short-term glucose starvation stimulated amantadine transport and inhibited TEA transport, but the effect was bicarbonate-modulated only for amantadine. cAMP analogues inhibited TEA transport while stimulating amantadine transport. This effect was additive to the effect of insulin, and the presence of bicarbonate affected the extent of the change. Our findings indicated that regulation of rOCT 1 and 2 was mediated by transmembrane adenylyl cyclase, and regulation of amantadine transport was mediated by soluble adenylyl cyclase, suggesting that intracellular microdomains of cAMP may be important in determining overall cellular transport for organic cations. Soluble adenylyl cyclase activity is known to be modulated by bicarbonate and lactate. These observations support our hypothesis and reconcile our previous studies demonstrating increased transport affinity for amantadine in the presence of bicarbonate and decreased transport affinity in the presence of lactate.
先前的研究表明，糖尿病大鼠肾脏组织中的金刚烷胺转运增加，而四乙基铵（TEA）转运减少。外源性胰岛素可逆转转运活性的变化。我们假设这种转运调节的差异是由于不同转运系统的差异调节所致。使用天然人胚肾皮质细胞（HEK293 细胞系）和大鼠有机阳离子转运体（rOCT）转染细胞来检验该假说。支持差异化调节的是，短期葡萄糖饥饿刺激金刚烷胺转运并抑制 TEA 转运，但这种作用仅对金刚烷胺是碳酸氢盐调节的。cAMP 类似物抑制 TEA 转运，同时刺激金刚烷胺转运。这种作用与胰岛素的作用相加，碳酸氢盐的存在影响变化的程度。我们的研究结果表明，rOCT1 和 2 的调节是通过跨膜腺苷酸环化酶介导的，而金刚烷胺转运的调节是通过可溶性腺苷酸环化酶介导的，这表明细胞内 cAMP 的微区可能对有机阳离子的整体细胞转运很重要。可溶性腺苷酸环化酶的活性已知受到碳酸氢盐和乳酸盐的调节。这些观察结果支持我们的假说，并调和了我们先前的研究结果，即在存在碳酸氢盐的情况下，金刚烷胺的转运亲和力增加，而在存在乳酸盐的情况下，转运亲和力降低。
