Flow dependence of metoprolol elimination in isolated perfused rat liver

The effect of blood flow rates on hepatic elimination of metoprolol (Met) was studied in a recirculating isolated perfused rat liver system with a constant infusion of Met into the reservoir. This design ensures that, at a steady state, the elimination rate of Met is a constant. The results showed that at flow rates of 10, 20, and 30 ml.min-1, the concentrations of Met entering the liver (Cin) were 7.6, 5.0, and 3.4 micrograms.ml-1 and the concentrations leaving the liver (Cout) were 1.2, 2.0, and 2.7 micrograms.ml-1, while the logarithmic average concentrations in hepatocytes (C) were 3.4, 3.2, and 3.0 micrograms.ml-1, respectively. It is concluded that the hepatic elimination of Met is flow-dependent, which is in accordance with the 'parallel tube' model.