Characterisation of penicillin G uptake in human small intestinal brush border membrane vesicles

BACKGROUND—Many β lactams are well absorbed by the small intestine, although the reasons for this are poorly understood. AIMS—To characterise the uptake of penicillin G into human small intestinal brush border membrane vesicles (BBMV) and to compare the uptake characteristics to those of rabbit BBMV. METHODS AND RESULTS—Uptake of penicillin G was studied in human BBMV. Penicillin G was actively transported into the lumen of BBMV via an H+ dependent, Na+ independent uptake system. The carrier mediated process was saturable and adhered to Michaelis-Menten kinetics (Vmax 52 nmol penicillin G per mg protein per 30 seconds, Km 13.9 mM). These results are similar to those previously reported in rabbit BBMV. CONCLUSIONS—It is suggested that penicillin G can be used as a model molecule for peptide and β lactam transport studies as it is cheap and readily available in isotopically labelled form. Furthermore, rabbit BBMV may be used as an acceptable substitute for human BBMV for the study of penicillin transport. Keywords: brush border membrane vesicles; β lactam; antibiotic uptake; oral administration; pH gradient