N-Glucosylation has been thought to be an important pathway for lower life forms but insignificant in mammals. Continued evidence suggests that in man the formation and/or urinary excretion of N-glucoside metabolites of barbiturates may be very important, is stereospecific and may play a complementary role to glucuronidation. Studies are designed to determine if the mouse is a suitable animal model for further study of the N-glucosylation pathway that has been observed in humans. Phenobarbital will be used in the initial studies since it is clinically the most important barbiturate used in humans. A sensitive radiochemical assay will be used to measure phenobarbital N-glucosylation in vitro using mouse liver microsomes and to characterize this N-glucosyltransferase enzyme. This assay will be used to determine what other endogenous and exogenous compounds can affect the N-glucosylation of phenobarbital. These studies will develop the first structure-substrate relationship for N-glucosylation in which absorption, distribution, metabolism and excretion will not be interfering variables. Metabolism studies using 14C-phenobarbital will be done in mice to determine if the mouse forms additional glycoside conjugates of phenobarbital. Additional studies are designed to determine the relationship of the PB N-glucoside pathway with the xenobiotic glucuronidation pathway by comparing the effect of sex, strain, xenobiotics and age on phenobarbital N-glucosylation versus p-nitrophenol glucuronidation. Finally, synthetic methodology will be developed to confirm structure and determine stereochemistry of new imide N-glucoside metabolites discovered during these studies.
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