Differential recognition of beta -lactam antibiotics by intestinal and renal peptide transporters, PEPT 1 and PEPT 2.

This study was initiated to determine if there are differences in the recognition of beta -lactam antibiotics as substrates between intestinal and renal peptide transporters, PEPT 1 and PEPT 2. Reverse transcription-coupled polymerase chain reaction and/or Northern blot analysis have established that the human intestinal cell line Caco-2 expresses PEPT 1 but not PEPT 2, whereas the rat proximal tubule cell line SKPT expresses PEPT 2 but not PEPT 1. Detailed kinetic analysis has provided unequivocal evidence for participation of PEPT 2 in SKPT cells in the transport of the dipeptide glycylsarcosine and the aminocephalosporin cephalexin. The substrate recognition pattern of PEPT 1 and PEPT 2 was studied with cefadroxil (a cephalosporin) and cyclacillin (a penicillin) as model substrates for the peptide transporters constitutively expressed in Caco-2 cells (PEPT 1) and SKPT cells (PEPT 2). Cyclacillin was 9-fold more potent than cefadroxil in competing with glycylsacosine for uptake via PEPT 1. In contrast, cefadroxil was 13-fold more potent than cyclacillin in competing with the dipeptide for uptake via PEPT 2. The substrate recognition pattern of PEPT 1 and PEPT 2 was also investigated using cloned human peptide transporters functionally expressed in HeLa cells. Expression of PEPT 1 or PEPT 2 in HeLa cells was found to induce H(+)-coupled cephalexin uptake in these cells. As was the case with Caco-2 cells and SKPT cells, the uptake of glycylsarcosine induced in HeLa cells by PEPT 1 cDNA and PEPT 2 cDNA was inhibitable by cyclacillin and cefadroxil. Again, the PEPT 1 cDNA-induced dipeptide uptake was inhibited more potently by cyclacillin than by cefadroxil, and the PEPT 2 cDNA-induced dipeptide uptake was inhibited more potently by cefadroxil than by cyclacillin. It is concluded that there are marked differences between the intestinal and renal peptide transporters in the recognition of beta -lactam antibiotics as substrates.

Penetration of ciclacillin into bronchial secretions.

The penetration of ciclacillin into bronchial secretions was investigated in 105 patients undergoing bronchoscopy after a single oral dose of 500 mg ciclacillin. Comparison was made with 26 patients who received 500 mg ampicillin by mouth. Over a 6 to 8 hour period, ciclacillin achieved significantly higher levels in bronchial secretions but no statistically significant difference between serum ampicillin and ciclacillin levels was detected.

Oral cyclacillin interacts with the absorption of oral ampicillin, amoxycillin, and bacampicillin.

The relative bioavailabilities of single oral doses of ampicillin, amoxycillin, and bacampicillin were compared with and without concomitant administration of a six-times higher molar dose of cyclacillin. As the absorption of cyclacillin has been shown to involve a capacity-limited transport system in animals, it was selected as the reference compound for the study. The treatments were given to 14 fasting volunteers using a randomized, complete crossover design. The drugs in plasma and urine were determined by liquid chromatography. Renal clearance was 17%, 10% and 19% lower when ampicillin, amoxycillin, and bacampicillin were given together with cyclacillin. Consequently, differences in the relative bioavailability were based on urinary recoveries assuming constant non-renal clearance. When amoxycillin was given with cyclacillin there was a 67% delay in the time of the plasma peak concentration, and an 8% lower urinary recovery than when it was given alone. There was a 50% and 33% delay in the tmax of ampicillin and bacampicillin when combined with cyclacillin; the urinary recovery of ampicillin in the combination was 10% lower but that of bacampicillin was similar. There was also a 20% delay in the tmax of cyclacillin when combined with amoxycillin. The differences in renal clearance indicate an interaction in the renal elimination of the drugs, but the effect was probably not the explanation for the marked shift in time of the absorption of these rapidly absorbed drugs. The results support the existence of a capacity-limited transport system for aminopenicillins in the human gut.

Kinetics and mechanism of in vitro uptake of amino-beta-lactam antibiotics by rat small intestine and relation to the intact-peptide transport system.

By utilizing the everted jejunum of rats, the initial uptake rates of several antibiotics were measured over a wide range of concentrations. The uptakes followed mixed-type kinetics involving saturable and non-saturable processes in parallel. The pertinent kinetic parameters for the uptake of each antibiotic were determined. The effect of cephalexin on the uptake of cyclacillin obeyed competitive inhibition kinetics, and the inhibition constant Ki was found to be equal to the Michaelis constant Kt for the uptake of cephalexin itself. In a similar way, the uptake of cephalexin was inhibited by cyclacillin. Uptakes of both cyclacillin and cephalexin were reduced significantly by several metabolic inhibitors. From the effect of temperature on the uptakes of cyclacillin and cephalexin, activation energies of 24.8 and 23.1 kcal/mole were obtained respectively. These results indicate the involvement of an active transport mechanism for cyclacillin and cephalexin. It was found that several dipeptides markedly inhibited the uptakes of cyclacillin and cefadroxil. Furthermore, the uptake of glycylglycine, a typical dipeptide, was inhibited by cyclacillin, cefadroxil, cephalexin, and cephradine. The kinetics of mutual inhibition of the uptakes of cyclacillin and glycylglycine were consistent with competitive-type inhibition. This is the first report which establishes, from a kinetic point of view, the involvement of a common transport system in the in vitro uptakes of the dipeptides and the antibiotics.

Intestinal absorption of several beta-lactam antibiotics. V. Effect of amino beta-lactam analogues and dipeptides on the absorption of amino beta-lactam antibiotics.

The absorption mechanism of amino beta-lactam antibiotics was investigated by using the whole small intestine of a rat. Mutual inhibition among amino beta-lactam analogues and the effects of dipeptides were studied. The influences of glycylglycine on the absorption of cephradine at the four different parts of intestine were also studied. Similarly to the case of cephalexin and cephradine, the absorption of amoxicillin was significantly inhibited by cyclacillin, cephradine, and cephalexin, but the absorption of ampicillin was not reduced by all tested antibiotics. In the experiments using dipeptides (6.0 mM), the absorption of cyclacillin was reduced significantly by glycylglycine, not by L-carnosine. And cephalexin absorption was influenced by L-carnosine (6.0, 10 mM), not by glycylglycine (6 mM). On the contrary, the absorption of cephradine was not reduced at all by these dipeptides. And from the experiment using the four different parts of intestine, it was shown that the transport interaction of glycylglycine with cephradine was observed in only one segment (the upper part of jejunum). These result suggest that the carrier-mediated transport system correlated to dipeptides participates only to a small degree in the common absorption mechanisms of these amino beta-lactam antibiotics.

Intestinal absorption mechanism of amphoteric beta-lactam antibiotics II: Michaelis-Menten kinetics of cyclacillin absorption and its pharmacokinetic analysis in rats.

The absorption of cyclacillin at pH 7.0 by the rat small intestine was investigated using in situ perfusion. At the lowest dose of 95 microgram/ml, the antibiotic disappearance was rapid and followed first-order kinetics, with the disappearance being 85% at 100 min. At the intermediate concentrations of 770 and 1200 microgram/ml, the disappearance after 100 min was 69 and 54%, respectively, and semilogarithmic plots clearly showed convex curvatures. At the highest concentration of 30 mg/ml, cyclacillin disappeared slowly from the perfusate, in an apparent first-order fashion. The disappearance was 26% after 100 min of perfusion and was similar in extent at 5.2 mg/ml. This concentration-time profile was satisfactorily fitted to the simultaneous Michaelis-Menten and first-order kinetic equations. The area under the blood concentration versus time curve (AUC) after a single intraduodenal dose of cyclacillin was almost consistent with the AUC after the equivalent intravenous dose (10 mg/kg). Additional evidence from a pharmacokinetic analysis of steady-state blood concentrations after constant infusion of cyclacillin through the portal vein and the small intestinal lumen indicated that cyclacillin absorption by the rat intestinal tissue at relatively low concentrations (less than 1 mg/ml) followed solely Michaelis-Menten kinetics. Cyclacillin may be transported by certain types of carrier-mediated mechanisms.

Comparative pharmacokinetics of cyclacillin and amoxicillin in infants and children.

Concentrations of cyclacillin in serum over a 6-h period were similar in fasted and milk-fed infants who received 25-mg/kg doses of cyclacillin suspension. Measured by the concentration in serum after oral administration of 15-mg/kg doses, cyclacillin was absorbed more rapidly, reached larger concentrations, and was cleared more promptly than was amoxicillin.

[Studies on the distributions of antibiotics in the oral tissues: Experimental staphylococcal infection in rats, and effect of serratiopeptidase on the distributions of antibiotics (author's transl)].

1) A focal infection was prepared by inoculation of staphylococci into rat gingiva. Then, concentrations in oral tissues (gingiva, tongue and masseter), serum and liver of the infected rats which were given ciclacillin, ampicillin, cephalexin and minocycline in a dose of 100 mg/kg p.o. were investigated and effects of serratiopeptidase (20 mg/kg) on these concentrations were studied. 2) Concentrations of ciclacillin in the oral tissues were approximately 10% of a serum level. A gingival concentration was elevated 8.5-fold by pretreatment with serratiopeptidase. A concentration in infected gingiva was 2.5-fold of that of another side of gingiva. 3) Concentrations of ampicillin in the oral tissues were approximately 15% of a serum level. A gingival concentration was elevated 5.7-fold by pretreatment with serratiopeptidase. A concentration in infected gingiva ws 2.2-fold of that of another side of gingiva. 4) Concentrations of cephalexin in the oral tissues were approximately 3 to 5-fold of a serum level except that in masseter. A gingival concentration was slightly elevated (1.1-fold) by pretreatment with serratiopeptidase. A concentration in infected gingiva was 1.7-fold of that of another side of gingiva. 5) Concentrations of minocycline in the oral tissues were 1.3 to 7.2-fold of a serum level. A gingival concentration was elevated 2.2-fold by pretreatment with serratipeptidase. A concentration in infected gingiva was 3.1-fold of that of another side of gingiva. 6) Gingival concentrations of antibiotics were higher than those of tongue and masseter and serratiopeptidase elevated gingival concentrations.

[Serum and tissue levels of ciclacillin]. / Serum- und Gewebsspiegel von Ciclacillin.

The level of Ciclacillin in serum, bone, and muscle was determined in 58 patients, subjected to bone surgery. 50 to 120 minutes after application, the drug concentration in bone was many times higher than in serum.

Absorption of amino penicillins from everted rat intestine.

1. Using an in vitro everted gut sac method based on that of Wilson & Wiseman (1954), a number of amino penicillins were tested in order to identify the involvement of any specialized transport mechanisms in their absorption across rat intestine. 2. Only one of the amino penicillins, cyclacillin (1-amino-cyclohexyl penicillin) was shown to be actively transported. The other penicillins appeared to diffuse passively across the intestine. 3. Cyclacillin was found to concentrate against a gradient at 37 degrees C but not at 19 degrees C. 4. Transport of cyclacillin across the mucosal membrane was saturated at mucosal concentrations greater than 1000 microgram/ml. 5. The rate of the forward flux of cyclacillin was many times that of its back flux. 6. No relationship between the active transport of cyclacillin and that of amino acids could be demonstrated.

[Studies on absorption and excretion of cyclacillin granules (vastcillin granules 'Takeda') (author's transl)].

Vastcillin granules 'Takeda', a cyclacillin (AC-PC) preparation for children were orally administered to nine children at a single dose of 10 mg/kg and its blood concentrations and urinary excretion were studied. From the results obtained, the following conclusions were obtained as to clinical dose and indications. (1) Absorption of AC-PC of Vastcillin granules is excellent . At 15 minutes after administration, 9.3 mcg/ml of AC-PC blood level was attained and its peak appeared 30 minutes after administration. The mean peak level was 17.6 mcg/ml.

Cyclacillin: microbiological and pharmacological properties and use in chemotherapy of infection - a critical appraisal.

The pharmacological and microbiological properties of cyclacillin were discussed and its usefulness in the management of a variety of infections was reviewed. The antibacterial spectrum and clinical utility of this agent generally parallels that of ampicillin, but there are minor differences in specificity with regard to individual microorganisms. The in vitro activity of cyclacillin against gram-negative pathogens varies greatly, the results fluctuating in accordance with the composition of the assay medium of method. The drug has demonstrated excellent therapeutic effectiveness against experimental infections produced by both gram-positive and gram-negative pathogens, thus making questionable a prediction of therapeutic effectiveness from in vitro susceptibility tests alone. Cyclacillin is more resistant to beta-lactamase hydrolysis than ampicillin, is much better absorbed when given by mouth and, as a result, the levels reached in the blood and in the urine are considerably higher than those obtained with the same dose of ampicillin. Cyclacillin produces fewer and milder side-effects than ampicillin.