INTESTINAL-ABSORPTION OF FLUORESCENCE-DERIVATIZED CATIONIC PEPTIDE 001-C8-NBD VIA ADSORPTIVE-MEDIATED TRANSCYTOSIS

The intestinal absorption of an intact oligopeptide was investigated i n rats using a synthetic cationic peptide, 001-C8 (H-MeTyr-Arg-MeArg-D -Leu-NH(CH2)(8)NH2). The peptide was coupled with 4-nitrobenzo-2-oxa-1 ,3-diazole (NBD) to prepare a fluorescence-labeled derivative 001-C8-N BD (H-MeTyr-Arg-MeArg-D-Leu-NH(CH2)(8)NH-NBD) for the purpose of quant ification, The degradation half-life of 001-C8-NBD in jejunal homogena te (1 mg/mL) was 99.5 min, which was significantly longer than that of natural leucine enkephalin (1.14 min). The absorption of 001-C8-NBD w as evaluated by the vascular-perfusion method. Intact 001-C8-NBD appea red in the blood time-dependently and the absorption volume at 30 min (2.75 +/- 0.14 mu L/cm intestine) was significantly larger than that o f [H-3]PEG 900 (0.88 +/- 0.13 mu L/cm intestine), of which membrane pe rmeability is very low. The absorption of 001-C8-NBD was greatly reduc ed by an adsorptive-mediated endocytosis inhibitor, protamine (10 mM). No inhibition of the absorption of [H-3]PEG 900 by protamine was obse rved. The intestinal absorption was also measured by an in vivo loop m ethod. The absorption clearance of 001-C8-NBD measured by this method (0.083 +/- 0.008 mu L/min/cm intestine) was comparable to that obtaine d by the vascular perfusion method (0.092 +/- 0.005 mu L/min/cm intest ine). All of these data suggested that 001-C8-NBD was absorbed as the intact oligopeptide in the intestine in vivo. Adsorptive-mediated tran scytosis is suggested to have enormous potential as an oral delivery s ystem for peptide and/or protein drugs. (C) 1998 Elsevier Science Ltd. All rights reserved.