Interaction of beta-lactam antibiotics with H+/peptide cotransporters in rat renal brush-border membranes
Takahashi, K.; Nakamura, N.; Terada, T.; Okano, T.; Futami, T.; Saito, H.; Inui, K.I.
Journal of Pharmacology and Experimental Therapeutics 286(2): 1037-1042
1998
ISSN/ISBN: 0022-3565 PMID: 9694966 Document Number: 495616
Two H+/peptide cotransporters, PEPT1 and PEPT2, are expressed in the kidney, mediating the renal tubular reabsorption of oligopeptides and beta-lactam antibiotics. We examined the interactions of beta-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 muM) 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 beta-lactam antibiotics with an a-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 alpha-amino group failed to show the trans-stimulation effect. It is concluded that amino-beta-lactam antibiotics at therapeutic concentrations interact predominantly with PEPT2 localized in the brush-border membranes of rat kidney.