Abstract
Two H+/peptide cotransporters, PEPT1 and PEPT2, are expressed in the kidney, mediating the renal tubular reabsorption of oligopeptides and β-lactam antibiotics. We examined the interactions of β-lactam antibiotics with peptide transporters in rat renal brush-border membranes by evaluating the inhibitory potencies of the antibiotics against glycylsarcosine transport. Western blot analysis revealed that PEPT1 and PEPT2 were expressed in the renal brush-border membranes with the apparent molecular masses of 75 and 105 kDa, respectively. Using renal brush-border membrane vesicles, the uphill transport of glycylsarcosine was observed in the presence of an inward H+ gradient and an inside-negative membrane potential. Two transport systems with high affinity (Km of 50 μM) and low affinity (Km of 1.2 mM) appeared kinetically to mediate the glycylsarcosine uptake. The inhibition constants of the antibiotics for glycylsarcosine transport were more closely correlated with those in stable LLC-PK1 cells transfected with rat PEPT2 rather than PEPT1 cDNA. The β-lactam antibiotics with an α-amino group showed trans-stimulation effects on the glycylsarcosine uptake, suggesting that these antibiotics and glycylsarcosine share a common peptide transporter. However, the antibiotics lacking an α-amino group failed to show thetrans-stimulation effect. It is concluded that amino-β-lactam antibiotics at therapeutic concentrations interact predominantly with PEPT2 localized in the brush-border membranes of rat kidney.
Footnotes
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Send reprint requests to: Professor Ken-ichi Inui, Department of Pharmacy, Kyoto University Hospital, Sakyo-ku, Kyoto 606-8507, Japan.
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↵1 This work was supported in part by a Grant-in-Aid for Scientific Research on Priority Areas of “Channel-Transporter Correlation” from the Ministry of Education, Science, and Culture of Japan, and by a Grant-in-Aid from Yamanouchi Foundation for Research on Metabolic Disorders.
- Abbreviations:
- HEPES
- N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid
- MES
- 2-(N-morpholino)-ethanesulfonic acid
- TRIS
- 2-amino-(2-hydroxymethyl)-1,3-propanediol
- Received December 3, 1997.
- Accepted April 13, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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