title: In vivo evidence for carrier-mediated uptake of beta-lactam antibiotics through organic anion transport systems in rat kidney and liver.
abstract: The transport mechanisms of beta-lactam antibiotics in the rat kidney and liver were studied with an in vivo tissue-sampling single-injection technique using [3H]benzylpenicillin [( 3H]PCG) as a substrate. Concentration-dependent uptake of [3H]PCG was observed in the kidney, and the in vivo kinetic parameters were estimated as follows: the maximum uptake rate (Jmax) was 6.88 mumol/min/g of kidney, MIchaelis constant (Kt) was 1.39 mM and nonsaturable first-order rate constant (kd) was 0.414 ml/min/g of kidney. The uptake of [3H]PCG was inhibited by organic anions but not by organic cations. Several beta-lactam antibiotics also reduced the uptake of [3H]PCG. Furthermore, the organic anion, probenecid, and beta-lactam antibiotic, cefpiramide, showed a dose-dependent inhibitory effect. These results suggest participation of an organic anion transport system in uptake of beta-lactam antibiotics across the renal plasma membrane. Saturable uptake of [3H]PCG was also observed in the liver and Jmax, Kt and Kd were estimated to be 3.62 mumol/min/g of liver, 3.59 mM and 0.223 ml/min/g of liver, respectively. The in vivo influx rate calculated from Jmax/Kt in the liver was 1.01 ml/min/g of liver and was close to the in vitro value, 1.54 ml/min/g of liver, estimated previously from isolated hepatocytes. Although dipeptides and organic cations showed no effect on the hepatic uptake of [3H]PCG, probenecid significantly reduced its uptake. Several beta-lactam antibiotics also reduced the uptake of [3H]PCG by the liver. These features of the hepatic uptake of beta-lactam antibiotics through an organic anion transport system are in agreement with the previous results obtained in isolated hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Faculty of Pharmaceutical Sciences, Kanazawa University, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tsuji
authors.forename: T
authors.initials: T
authors.lastname: Terasaki
authors.forename: I
authors.initials: I
authors.lastname: Tamai
authors.forename: K
authors.initials: K
authors.lastname: Takeda
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics* / Q000494:pharmacology; D001692:Biological Transport; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010400:Penicillin G / Q000493:pharmacokinetics; D011339:Probenecid / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D010130:p-Aminohippuric Acid / Q000493:pharmacokinetics
chemical_list: D000900:Anti-Bacterial Agents; D011339:Probenecid; D010400:Penicillin G; D010130:p-Aminohippuric Acid