MODIFICATION OF HEPATIC CYTOCHROME-P450 PROFILE BY COCAINE-INDUCED HEPATOTOXICITY IN DBA 2 MOUSE/

Previous studies in our laboratory have shown that a hepatotoxic dose of cocaine increases coumarin 7-hydroxylase activity in male DBA/2 mou se liver. In the present study, the dose- and time-dependent responses of the hepatic CYP2A4/5 complex to cocaine-induced liver damage were studied. Cocaine increased CYP2A4/5 levels in a dose-dependent manner. The maximal increases in coumarin 7-hydroxylase activity (4-fold), mi crosomal CYP2A4/5 content (3-fold) and steady-state mRNA levels (10-fo ld) were observed at 24 h after administration of a single dose of 60 mg/kg cocaine coinciding with morphologically detectable diffuse liver damage, while the total P450 content was not changed. 3 and 5 days af ter the daily administration of cocaine severe, mainly pericentral (zo ne III of Rappaport), liver damage was apparent in parallel with a cle ar decline in CYP2A4/5 mRNA, protein content and coumarin 7-hydroxylas e activity. After 5 days of treatment, CYP2A5 still remained at a very low level but an induction in CYP2B10 protein and related pentoxyreso rufin O-dealkylase activity was observed. No marked changes in microso mal CYP2Cx and CYP1A1/2 contents or associated activities were observe d. Dimethylnitrosamine N-demethylase activity, a marker for CYP2E1, de creased in parallel with increased cocaine dose and time and the sever ity of liver damage. Our results demonstrate that (i) administration o f cocaine causes a clear but transient increase in the expression of C yp2a-4/5 gene complex prior to overt liver damage and (ii) microsomal CYP2B10 and related 7-pentoxyresorufin O-dealkylase activity is marked ly increased in animals treated for 5 days with cocaine concomitantly with the decrease in other monooxygenases indicating an association of coumarin 7-hydroxylase activity with liver injury and different roles for coumarin 7-hydroxylase and 7-pentoxyresorufin O-dealkylase activi ties in cocaine hepatotoxicity.