Depletion of hepatic UDP-glucuronic acid by drugs that are glucuronidated
Howell, S.R.; Hazelton, G.A.; Klaassen, C.D.
Journal of Pharmacology and Experimental Therapeutics 236(3): 610-614
1986
ISSN/ISBN: 0022-3565 PMID: 3081704 Document Number: 283848
Salicylamide, clofibric acid, valproic acid and chloramphenicol are all known to be glucuronidated. The effects of these compounds on the hepatic concentration of UDP-glucuronic acid, the cosubstrate for glucuronidation, were studied in mice and found to lower hepatic UDP-glucuronic acid in a dose- and time-dependent fashion. Valproic acid, chloramphenicol, salicylamide and clofibric acid depleted hepatic UDP-glucuronic acid significantly at dosages as low as 0.5, 0.5, 0.75 and 4.0 mmol/kg, respectively. Hepatic UDP-glucuronic acid was decreased by 90% by valproic acid, 91% by chloramphenicol, 98% by salicylamide and 41% by clofibric acid (after dosages of 4, 2, 1 and 5 mmol/kg, respectively). UDP-glucuronic acid was depleted maximally by 15 after drug administration. Salicylamide also was used as a model compound to study the effect of drug loading on the hepatic concentrations of UDP-glucose and glycogen, precursors of UDP-glucuronic acid. It was found that, in addition to UDP-glucuronic acid, salicylamide (4 mmol/kg) also depleted UDP-glucose and glycogen by about 50%. These data suggest that large drug loads cause an increase flux through the glucuronic acid pathway and that hepatic UDP-glucuronic acid is consumed more rapidly than it is produced.