Carrier-mediated transport systems for aminopenicillins in rat small intestine.

Abstract

The absorption of aminopenicillins from rat small intestine was investigated by using the in situ oerfsion technique. Carrier-mediated teansport systems were demonstrated for amonxicillin and cyclacillin. The absorption of amoxicillin and cyclacillin was saturable and inhibited by the short term pretreatment of the intestine with alow concentration of HgCl2. The two penicillins inhibited intestinal absorption to each other. The simultaneous perfusion of dioeotides. L-phenylalanylglycine and glycycine, inhibited the absorption of cyclacillin but not of amoxicillin. Furthermore, only cyclacillin was shown to concentrate aganst agrabient. These data are consistent with the presence of two carrier systems for the active transport of cyclacillin in the intestinal mucosa : one which can be blocked by amoxicillin, and the other by bipeptides. Amoxicillin may be transported by the facilitated diffusion mechanism, the carrier of which seems to be common to one of the carrier systems for cyclacillin transport. No evidence of carrier-mediated transport of a, picillin could be found.