INDUCTION OF RAT HEPATIC P4501A1 BY ORGANIC EXTRACTS FROM AIRBORNE PARTICULATE MATTER IN SANTIAGO, CHILE

1. Organic extracts from particulate matter collected in downtown Sant iago, Chile, in 1990 were administered to female Wistar rats. 2. Extra cts shifted the maximal absorption wavelength P450 spectra of the redu ced-CO complex of hepatic microsomal P450 from 450 to 448 nm, and enha nced the total content of P450. In addition, substantial increases in aryl hydrocarbon hydroxylase, ethoxyre sorufin O-deethylase and ethoxy coumarin O-deethylase activities were observed, whereas aminopyrine N- demethylase activity was not affected by treatment. 3. Western blottin g using polyclonal antibodies against P4501A isozymes showed the appea rance of a distinct and intense P4501A1 band in microsomes from rat pr etreated with air particle extracts, and was not observed in microsome s from control rat. On the other hand, the intensity of the P4501A2 is oenzyme was apparently not affected. 4. These findings suggest that th e organic extracts from airborne particulate matter modify the composi tion of rat liver P450 isozymes by inducing those isoforms responsible for the activation of precarcinogenic to carcinogenic agents.