RAT SERUM-ALBUMIN MODIFIED BY DIFLUNISAL ACYL GLUCURONIDE IS IMMUNOGENIC IN RATS

Acyl glucuronide metabolites of carboxylic acid drugs such as the sali cylate derivative diflunisal (DF) have been shown to react with protei ns in vitro and in vivo to produce covalent adducts. Such attachment o f foreign compounds to endogenous molecules could be associated with t oxic and/or immune consequences. In this study we have injected rats w ith rat serum albumin (RSA) modified (a) by DF using a carbodiimide re agent (--> DF-RSA-I, 4.9 mu g DF/mg RSA) and (b) by incubation with DF acyl glucuronide (DAG) and its rearrangement isomers (iso-DAG) (--> D F-RSA-II, 0.34 mu g DF/mg RSA). All of the six rats injected with DF-R SA-I produced antibodies reactive with DF-modified keyhole limpet hemo cyanin (KLH), the coating protein used in the ELISA. Three out of six animals injected with DF-RSA-II generated similar antibodies. Cross-re activity with other non-steroidal anti-inflammatory drugs (NSAIDs) suc h as naproxen and ketoprofen (as the free drugs) was not observed. Thi s study shows that a self protein covalently modified by incubation wi th DAG and iso-DAG is immunogenic in rats. The data thus support the h ypothesis that covalent modification of macromolecules by acyl glucuro nide metabolites of acidic drugs in vivo can lead to the production of circulating antibodies which may be involved in aberrant immune respo nses; such as drug hypersensitivity.