Relevance of PepT1 in the intestinal permeability and oral absorption of cefadroxil

Abstract

Purpose: To determine the contribution of intestinal PepT1 on the permeability and oral absorption of the β-lactam antibiotic drug cefadroxil.

Methods: The effective permeability (P eff ) of cefadroxil was evaluated in wild-type and PepT1 knockout mice following in situ single-pass intestinal perfusions. The plasma concentration-time profiles of cefadroxil were also examined after oral gavage.

Results: The P eff (cm/s) of cefadroxil in wild-type mice was 0.49 × 10(-4) in duodenum, 0.80 × 10(-4) in jejunum, 0.88 × 10(-4) in ileum and 0.064 × 10(-4) in colon. The P eff (cm/s) in PepT1 knockout mice was significantly reduced in small intestine, but not in colon, as shown by values of 0.003 × 10(-4), 0.090 × 10(-4), 0.042 × 10(-4) and 0.032 × 10(-4), respectively. Jejunal uptake of cefadroxil was saturable (Km = 2-4 mM) and significantly attenuated by the sodium-proton exchange inhibitor 5-(N,N-dimethyl)amiloride. Jejunal permeability of cefadroxil was not affected by L-histidine, glycine, cephalothin, p-aminohippurate or N-methylnicotinamide. In contrast, cefadroxil permeability was significantly reduced by glycylproline, glycylsarcosine, or cephalexin. Finally, PepT1 ablation resulted in 23-fold reductions in peak plasma concentrations and 14-fold reductions in systemic exposure of cefadroxil after oral dosing.

Conclusions: The findings are definitive in demonstrating that PepT1 is the major transporter responsible for the small intestinal permeability of cefadroxil as well as its enhanced oral drug performance.

Fig. 1

Concentration-dependent uptake of cefadroxil (0.01-25 mM) in the jejunum of wild-type mice where C_in is the inlet concentration of cefadroxil in perfusate (A) and C_w is the estimated concentration of cefadroxil at the membrane wall (B), and as represented by a Woolf-Augustinnson-Hofstee transformation (C). All studies were performed in pH 6.5 buffer. Data are reported as mean ± SE (n=4-8).

Fig. 1

Concentration-dependent uptake of cefadroxil (0.01-25 mM) in the jejunum of wild-type mice where C_in is the inlet concentration of cefadroxil in perfusate (A) and C_w is the estimated concentration of cefadroxil at the membrane wall (B), and as represented by a Woolf-Augustinnson-Hofstee transformation (C). All studies were performed in pH 6.5 buffer. Data are reported as mean ± SE (n=4-8).

Fig. 1

Concentration-dependent uptake of cefadroxil (0.01-25 mM) in the jejunum of wild-type mice where C_in is the inlet concentration of cefadroxil in perfusate (A) and C_w is the estimated concentration of cefadroxil at the membrane wall (B), and as represented by a Woolf-Augustinnson-Hofstee transformation (C). All studies were performed in pH 6.5 buffer. Data are reported as mean ± SE (n=4-8).

Fig. 2

Effective permeability of 10 μM cefadroxil in different intestinal regions of wild-type and PepT1 knockout mice. All studies were performed in pH 6.5 buffer. Data are reported as mean ± SE (n=4-8). Treatment groups with the same capital letter (A or B) are not statistically different.

Fig. 3

Proton-dependent permeability of 10 μM cefadroxil in the jejunum of wild-type mice as a function of pH 5.5 to 7.5 (A) and 0.1 mM of the sodium-proton inhibitor dimethyl-amiloride (DMA), at pH 6.5 (B). Data are reported as mean ± SE (n=4-8). ** p < 0.01, as compared to the control value.

Fig. 3

Proton-dependent permeability of 10 μM cefadroxil in the jejunum of wild-type mice as a function of pH 5.5 to 7.5 (A) and 0.1 mM of the sodium-proton inhibitor dimethyl-amiloride (DMA), at pH 6.5 (B). Data are reported as mean ± SE (n=4-8). ** p < 0.01, as compared to the control value.

Fig. 4

Permeability of 10 μM cefadroxil in the jejunum of wild-type mice when co-perfused with potential inhibitors (25 mM). All studies were performed in pH 6.5 buffer. Data are reported as mean ± SE (n=4-8). **p < 0.01 and ***p < 0.001, as compared to the control value.

Fig. 5

Plasma concentration-time profiles of cefadroxil in wild-type and PepT1 knockout mice following a 44.5 nmol/g oral dose of drug. Data are reported as mean ± SE (n=3) in which the y-axis is displayed on a linear scale (A) and on a logarithmic scale (B).

Fig. 5

Plasma concentration-time profiles of cefadroxil in wild-type and PepT1 knockout mice following a 44.5 nmol/g oral dose of drug. Data are reported as mean ± SE (n=3) in which the y-axis is displayed on a linear scale (A) and on a logarithmic scale (B).