Use of primary rat hepatocytes in the gel entrapment culture to predict in vivo biliary excretion.

In vitro models have been widely used in characterizing the hepatobiliary elimination of compounds. However, the application of in vitro models is often limited by their imperfect simulation of in vivo situations. The current paper aims to introduce the gel entrapment culture of rat hepatocytes as an alternative method for measuring hepatobiliary transport, with the sandwich culture of rat hepatocytes set as the control. First, the culture conditions of the gel-entrapped hepatocytes were modified to enhance hepatic transport function. When cultured under optimal conditions, i.e. the collagen concentration was set to 0.6 mg/mL and the regular Williams' E medium was supplemented with epidermal growth factor, the hepatocytes maintained much higher hepatic transporter gene expression levels and transport activities than that in regular gel entrapment and sandwich culture. Compared with the actual values in rats, the predicted intrinsic biliary clearance (CL(bile,int,predicted)) of the 10 model compounds in the optimized gel entrapment culture showed a high correlation coefficient squared (R(2)) of 0.94, with the majority falling within the two-fold error range of the in vivo values, which was much better than the comparable sandwich culture. All of these results indicate that the optimized gel entrapment culture of hepatocytes is a suitable approach for estimating in vivo biliary excretion.