Chitosan Influences the Expression of P-gp and Metabolism of Norfloxacin in Grass Carp

Abstract

The aim of this study was to investigate the relationship between the administration of chitosan (CTS), expression of permeability glycoprotein (P-gp), and the metabolism of norfloxacin (NOR) in Grass Carp Ctenopharyngodon idella. Fish were administrated with a single dose of either NOR, CTS, 1:5 NOR–CTS or 1:10 NOR–CTS. The P-gp expression was analyzed by immunohistochemistry and real time-PCR. The concentration of NOR was determined using HPLC. The mRNA and protein expression of P-gp in the fish intestine was significantly enhanced following a single dosage of 40 mg/kg NOR, and peak expression occurred at 3 h after drug administration (P < 0.05). A single dosage of both 1:5 NOR–CTS and 1:10 NOR–CTS reduced the intestinal P-gp expression to levels significantly lower than that from NOR alone (P < 0.05), but significantly higher than that from the control (P < 0.05). Interestingly, CTS alone also led to a slight decrease in P-gp expression. In addition, pharmacokinetic assays revealed a marked increase in area under the curve (AUC) of NOR with 1:5 and 1:10 NOR–CTS, by approximately 1.5-fold and threefold, respectively. Finally, the relative bioavailability of NOR after a single oral dosage of 1:5 and 1:10 NOR–CTS was enhanced to 148.02% and 304.98%, respectively. In this study, we demonstrated that the transmembrane glycoprotein P-gp regulates NOR metabolism in the intestine of Grass Carp, suggesting that NOR may be a direct substrate of P-gp. More importantly, we showed that CTS can inhibit P-gp expression in a dose-dependent manner and improve the relative bioavailability of NOR in this species.

Received August 25, 2014; accepted November 12, 2014

ACKNOWLEDGMENTS

This study was supported by the 863 Program (grant 2011AA10A216), the Special Fund for Agro-scientific Research in the Public Interest (grant 201203085), and the Key Project of Science and Technology of the Shanghai Agriculture Committee. There is no conflict of interest related to this manuscript.