Formation of a beta-glucuronidase-resistant glucuronide conjugate of digitoxin by dog liver microsomes

MC Castle

Department of Pharmacology, Eastern Virginia Medical School, Norfolk 23501.

The aim of these studies was to characterize the glucuronide conjugates of digitoxin and digitoxigenin monodigitoxoside (DMD) produced by liver microsomes from the dog with respect to hydrolysis by beta- glucuronidase and to behavior on HPLC. These results have been compared with studies of conjugates produced by liver microsomes from the rat. Glucuronidation was similar with both substrates with dog microsomes, whereas rat microsomes formed the glucuronide with DMD but not with digitoxin. The DMD glucuronide from both species was completely hydrolyzed by beta-glucuronidase, but no hydrolysis of digitoxin glucuronide was detected. The digitoxin glucuronide was hydrolyzed by a buffer at pH 1.5 but not at pH 10. After acid hydrolysis, the major products appear to be digitoxigenin and DMD glucuronide. These results suggest that glucuronidation of certain drugs by the dog is quite different from that of other species and that the dog may be the only species that possesses a glucuronosyltransferase capable of forming a glucuronide conjugate with digitoxin. The dog also has a glucuronosyltransferase, similar to that in the rat, which is responsible for glucuronidation of DMD. Whether this represents a single glucuronosyltransferase or two different enzymes remains to be elucidated.

Volume 21, Issue 6, pp. 1147-1150, 11/01/1993
Copyright © 1993 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				D. Pless, J. N. Gouze, C. Senay, R. Herber, P. Leroy, V. Barberousse, S. Fournel-Gigleux, and J. Magdalou Characterization of the UDP-Glucuronosyltransferases Involved in the Glucuronidation of An Antithrombotic Thioxyloside in Rat and Humans Drug Metab. Dispos., May 1, 1999; 27(5): 588 - 595. [Abstract] [Full Text]