Chem.-Biol. Interactions, 79 (1991) 79--89 79 Elsevier ScientificPublishers Ireland Ltd. EFFECT OF VARIOUS CHEMICALS ON THE ALDEHYDE DEHYDROGENASE ACTIVITY OF THE RAT LIVER CYTOSOL MARIOS MARSELOSand VASILIS VASILIOU Department of Pharmacology, Medical School. University of loannin~l. P.O. Box 1186. GR-45110 loannina (Greece) (Received October 27th, 1990) (Revision received March 8th, 1991) (Accepted March 15th, 1991) SUMMARY The cytosolic activity of aldehyde dehydrogenase (ALDH) was studied in the rat liver, after acute administration of various carcinogenic and chemically related compounds. Male Wistar rats were treated with 27 different chemicals, including polycyclic aromatic hydrocarbons, aromatic amines, nitrosamines, azo dyes, as well as with some known direct-acting carcinogens. The cytosolic ALDH activity of the liver was determined either with propionaldehyde and NAD (P/NAD), or with benzaldehyde and NADP (B/NADP). The activity of ALDH re- mained unaffected after treatment with 1-naphthylamine, nitrosamines and also with the direct-acting chemical carcinogens tested. On the contrary, polycyclic aromatic hydrocarbons, polychlorinated biphenyls (Arochlor 1254) and 2-naphthylamine produced a remarkable increase of ALDH. In general, the response to the effectors was disproportionate between the two types of enzyme activity, being much in favour for the B/NADP activity. This fact resulted to an inversion of the ratio B/NADP vs. P/NAD, which under constitutive conditions is lower than 1. In this respect, the most potent compounds were found to be polychlorinated biphenyls, 3-methylcholanthrene, benzo(a)pyrene and 1,2,5,6-dibenzoanthracene. Our results suggest that the B/NADP activity of the soluble ALDH is greatly induced after treatment with compounds possessing aromatic ring(s) in their molecule. It is not known, if this response of the hepatocytes is related with the process of chemical carcinogenesis. Key words: Aldehyde dehydrogenase -- Induction -- Carcinogens -- Liver -- Rat Correspondence to: M. Marselos,Professorof Pharmacology,Departmentof Pharmacology., Medical School, GR-451 10 Ioannina, Greece. 0009-2797/91/$03.50 © 1991 Elsevier ScientificPublishers Ireland Ltd. Printed and Published in Ireland