Tamai I, Nakanishi T, Hayashi K, Terao T, Sai Y, Shiraga T, Miyamoto K, Takeda E, Higashida H, Tsuji A
Faculty of Pharmaceutical Sciences, School of Medicine, Kanazawa University, Japan.
J Pharm Pharmacol. 1997 Aug;49(8):796-801. doi: 10.1111/j.2042-7158.1997.tb06115.x.
Although recent evidence suggests that certain beta-lactam antibiotics are absorbed via a specific transport mechanism, its nature is unclear. To confirm whether peptide transport in the rat can be largely ascribed to the intestinal oligopeptide transporter PepT1, the transporter has been functionally characterized and its significance in the intestinal absorption of beta-lactam antibiotics was evaluated. For evaluation of transport activity complementary RNA (cRNA) of rat PepT1 was synthesized in-vitro and expressed in Xenopus laevis oocytes. cRNA induced uptake of several beta-lactam antibiotics and the dipeptide [14C]glycylsarcosine; this was specifically inhibited by various dipeptides and tripeptides but not by their constituent amino acids or by tetra- or pentapeptides. The transport activity of PepT1 for beta-lactam antibiotics correlated well with their in-vivo intestinal transport and absorption. Furthermore, mutual inhibitory effects on uptake were observed between glyclsarcosine and beta-lactam antibiotics. Hybrid depletion of the functional expression of rat PepT1 in oocytes injected with rat intestinal epithelial total mRNA was studied using an antisense oligonucleotide corresponding to the 5'-coding region of PepT1. In oocytes injected with rat mRNA pre-hybridized with the antisense oligonucleotide against rat PepT1, the uptake of [14C]glycylsarcosine was almost completely abolished, whereas its uptake was not influenced by a sense oligonucleotide for the same region of PepT1. Similarly, the uptake of beta-lactam antibiotics was also reduced by the antisense oligonucleotide against rat PepT1. These results demonstrate that the intestinal proton-coupled oligopeptide transporter PepT1 plays a predominant role in the carrier-mediated intestinal absorption of beta-lactam antibiotics and native oligopeptides in the rat.
尽管最近有证据表明某些β-内酰胺类抗生素是通过特定的转运机制被吸收的，但其本质尚不清楚。为了确定大鼠体内的肽转运是否主要归因于肠道寡肽转运体PepT1，对该转运体进行了功能表征，并评估了其在β-内酰胺类抗生素肠道吸收中的意义。为了评估转运活性，在体外合成了大鼠PepT1的互补RNA（cRNA）并在非洲爪蟾卵母细胞中表达。cRNA诱导了几种β-内酰胺类抗生素和二肽[14C]甘氨酰肌氨酸的摄取；这被各种二肽和三肽特异性抑制，但不受其组成氨基酸或四肽或五肽的抑制。PepT1对β-内酰胺类抗生素的转运活性与其体内肠道转运和吸收密切相关。此外，观察到甘氨酰肌氨酸和β-内酰胺类抗生素之间对摄取的相互抑制作用。使用与PepT1的5'-编码区相对应的反义寡核苷酸，研究了在注射大鼠肠上皮总mRNA的卵母细胞中大鼠PepT1功能表达的杂交缺失。在注射了与针对大鼠PepT1的反义寡核苷酸预杂交的大鼠mRNA的卵母细胞中，[14C]甘氨酰肌氨酸的摄取几乎完全被消除，而其摄取不受针对PepT1相同区域的正义寡核苷酸的影响。同样，针对大鼠PepT1的反义寡核苷酸也降低了β-内酰胺类抗生素的摄取。这些结果表明，肠道质子偶联寡肽转运体PepT1在大鼠体内载体介导的β-内酰胺类抗生素和天然寡肽的肠道吸收中起主要作用。
