Terada T, Sawada K, Ito T, Saito H, Hashimoto Y, Inui K
Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Kyoto 606 - 8507, Japan.
Am J Physiol Renal Physiol. 2000 Nov;279(5):F851-7. doi: 10.1152/ajprenal.2000.279.5.F851.
We examined the peptide transport activity in renal basolateral membranes. [(14)C]glycylsarcosine (Gly-Sar) uptake in rat renal cortical slices was saturable and inhibited by excess dipeptide and aminocephalosporin cefadroxil. When several renal cell lines were screened for the basolateral peptide transport activity, Madin-Darby canine kidney (MDCK) cells were demonstrated to have the greatest transport activity. [(14)C]Gly-Sar uptake across the basolateral membranes of MDCK cells was inhibited by di- and tripeptide and decreased with decreases in extracellular pH from 7.4 to 5.0. The Michaelis-Menten constant value of [(14)C]Gly-Sar uptake across the basolateral membranes of MDCK cells was 71 microM. The basolateral peptide transporter in MDCK cells showed several different [(14)C]Gly-Sar transport characteristics in growth dependence, pH profile, substrate affinity, and sensitivities to chemical modifiers from those of the apical H(+)-peptide cotransporter of MDCK cells. The findings of the present investigation indicated that the peptide transporter was expressed in the renal basolateral membranes. In addition, from the functional characteristics, the renal basolateral peptide transporter was suggested to be distinguishable from known peptide transporters, i.e., H(+)-peptide cotransporters (PEPT1 and PEPT2) and the intestinal basolateral peptide transporter.
我们检测了肾基底外侧膜中的肽转运活性。大鼠肾皮质切片对[¹⁴C]甘氨酰肌氨酸（Gly-Sar）的摄取具有饱和性，并受到过量二肽和氨基头孢菌素头孢羟氨苄的抑制。在对几种肾细胞系进行基底外侧肽转运活性筛选时，发现麦迪逊-达比犬肾（MDCK）细胞具有最强的转运活性。MDCK细胞基底外侧膜对[¹⁴C]Gly-Sar的摄取受到二肽和三肽的抑制，并且随着细胞外pH从7.4降至5.0而降低。MDCK细胞基底外侧膜对[¹⁴C]Gly-Sar摄取的米氏常数为71微摩尔。MDCK细胞中的基底外侧肽转运体在生长依赖性、pH曲线、底物亲和力以及对化学修饰剂的敏感性等方面，表现出与MDCK细胞顶端H⁺-肽共转运体不同的[¹⁴C]Gly-Sar转运特性。本研究结果表明，肽转运体在肾基底外侧膜中表达。此外，从功能特性来看，肾基底外侧肽转运体被认为与已知的肽转运体，即H⁺-肽共转运体（PEPT1和PEPT2）以及肠基底外侧肽转运体不同。
