Cephalosporin organic cation transport

The carrier-mediated uptake of p-aminohippuric acid (PAH) into BBMV (Figure 7) and PAH accumulation by renal cortical slices [69,77] were also significantly reduced by CPH treatment (1200 mg/kg/d for 3d). Furthermore, the transport of other cephalosporins across the renal brush border membrane is also affected by CPH-treatment the uptake of cephalexin and cefotiam into BBMV was greatly reduced whereas the uptake of CPH remained unaffected [77]. Secretion of cephalosporins across the brush border membrane is assumed to occur by the PAH-system as well as by the organic cation/H+-antiporter [127,133]. Reabsorption of many cephalosporins is performed by the dipeptide transport system [69, 133]. The unaffected uptake of CPH into BBMV from CPH-treated rats indicates that CPH is transported by a system different from the... 

The first step is the activation, i.e., protonation of the carrier. The active proto-nated carrier can react with cephalosporin anion (P ) to form a complex AHP which is soluble in organic phase. The transport of anion from one phase to another requires the co-transport of cation (H+). The reaction is instantaneous and the mass transport of the ionic species controls the reaction rate. 

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