Application of a loading wash-out method for investigating the hepatocellular efflux of a hepatically-generated metabolite, morphine-3-glucuronide

J Pharm Pharmacol. 1999 Nov;51(11):1289-97. doi: 10.1211/0022357991776868.


Previous studies using the rat isolated perfused liver demonstrated that the hepatic disposition of morphine-3-glucuronide is membrane permeability-rate limited, and that the movement of the metabolite across hepatic sinusoidal and canalicular membranes is partly via carrier-mediated transport systems. As a consequence of the membrane permeability-limitation, the biliary excretion of hepatically-generated morphine-3-glucuronide is much more efficient than that of morphine-3-glucuronide reaching the liver via the vasculature. We have quantitated the cellular efflux kinetics (cell-to-blood and cell-to-bile) of morphine-3-glucuronide in the rat isolated perfused liver using a loading wash-out design. In the 'loading' phase, morphine was infused into the liver (2.7 microM) and the biliary excretion and sinusoidal efflux of morphine-3-glucuronide was assessed under steady-state conditions. Subsequently, the infusion was stopped and the concentration vs time profile of morphine-3-glucuronide in outflow perfusate (the wash-out phase) was determined. A physiologically-based pharmacokinetic model was used to determine the rate-constants for the movement of hepatically-generated morphine-3-glucuronide into the sinusoidal and canalicular spaces of the liver, and the associated membrane permeability terms. The mean (+/-s.d.) rate constants for the biliary excretion and sinusoidal efflux of morphine-3-glucuronide were determined to be 0.160 +/- 0.043 and 0.169 +/- 0.068 min(-1), respectively, and the corresponding membrane permeability parameters were 1.12 and 1.18 mL min(-1), respectively. The sinusoidal membrane permeability term was significantly less than hepatic blood flow in the rat. The volume of distribution of hepatically-generated morphine-3-glucuronide (207.5 +/- 74.8 mL) was found to be approximately 50-times the intracellular space of the rat liver, suggesting that hepatically-generated morphine-3-glucuronide accumulates within hepatocytes. The results indicate that hepatically-generated morphine-3-glucuronide undergoes intracellular accumulation, probably as a consequence of poor membrane permeability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Animals
  • Area Under Curve
  • Bile / metabolism
  • Female
  • In Vitro Techniques
  • Liver / chemistry
  • Liver / cytology
  • Liver / metabolism*
  • Models, Biological
  • Morphine Derivatives / chemistry
  • Morphine Derivatives / pharmacokinetics*
  • Oxygen Consumption / drug effects
  • Perfusion
  • Rats
  • Rats, Sprague-Dawley


  • Morphine Derivatives
  • morphine-3-glucuronide