Kinetics of hepatic transport of 4-methylumbelliferone in rats. Analysis by multiple indicator dilution method
Hepatic elimination of 4-methylumbelliferone (4-MU), which has been used as a model compound for conjugative metabolism, was studied by means of a multiple indicator dilution (MID) method in the isolated perfused rat liver. Using this method, three intrinsic hepatic clearances, CLint,inf, CLint,eff, and CLint,seq, which represent the influx, efflux, and sequestration processes, respectively, were obtained. When the dose was increased from a low dose (50 micrograms/rat liver) to a high dose (3000 micrograms/rat liver), the hepatic availability of 4-MU increased from 0.11 to 0.73. With increasing dose, the CLint,eff value increased approximately two times, while the CLint,seq value decreased to approximately one-third. The remarkable dose dependence of hepatic availability was due to nonlinearity in both CLint,eff and CLint,seq values. However, the CLint,inf value was almost independent of dose. The dose-dependent change in CLint,seq might be explained by the saturation of conjugative metabolism of 4-MU, while the increase in the CLint,eff value with increasing dose might be partly explained by the nonlinear tissue binding of 4-MU, since the tissue unbound fraction determined by an ultrafiltration method using liver homogenate increased approximately 1.5 times at higher concentration of 4-MU compared to that at lower concentrations. In addition, based on a comparison of the individual intrinsic clearances, i.e., CLint,inf, CLint,eff, and CLint,seq, the major determining process of the apparent hepatic intrinsic clearance of 4-MU is thought to be the sequestration process at the high dose. However, at the low dose, the membrane transport process (influx and efflux processes) as well as the sequestration process also determine the apparent hepatic intrinsic clearance.
- Research Organization:
- Univ. of Tokyo, Japan
- OSTI ID:
- 5977564
- Journal Information:
- J. Pharmacokinet. Biopharm.; (United States), Vol. 15:1
- Country of Publication:
- United States
- Language:
- English
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COUMARIN
MEMBRANE TRANSPORT
METABOLISM
BIOCHEMICAL REACTION KINETICS
CLEARANCE
DOSE-RESPONSE RELATIONSHIPS
ERYTHROCYTES
IN VITRO
ISOTOPE DILUTION
LIVER
PERFUSED ORGANS
RATS
ANIMALS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY
BODY FLUIDS
DIGESTIVE SYSTEM
ESTERS
GLANDS
HETEROCYCLIC COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LACTONES
MAMMALS
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ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANS
PYRANS
REACTION KINETICS
RODENTS
TRACER TECHNIQUES
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550501* - Metabolism- Tracer Techniques