The objective of this study was to assess possible interaction between kurosu (japanese unpolished rice vinegar) and Pglycoprotein (P-gp), using rhodamine 123 (Rho-123) and glibenclamide (GB) as known P-gp substrates. The absorption of the drugs was investigated using an in situ loop technique. Three 10-cm loops were created in the rat small intestine - in the duodenal, jejunal, and ileal regions. Then, a test solution was introduced into each loop and its disappearance rate after 30 min was determined.
In the presence of kurosu, Rho-123 absorption markedly increased in the 3 regions. Although the lipophilicity of GB was greater than that of tolbutamide (TB), GB absorption was much less than that of TB in the 3 regions, which implied that an efflux transporter restricted GB absorption. However, typical P-gp inhibitors such as verapamil and cyclosporin A slightly increased GB absorption. Also, the enhancing effect of kurosu on GB absorption was limited.
The present results suggest that some components of kurosu are capable of strongly interfering with P-gp function in the intestine and increasing the absorption of P-gp substrates. Our data also imply that an efflux transporter other than P-gp is involved in the low absorption of GB.
