FASTING FOR LESS-THAN 24 H INDUCES CYTOCHROME-P450 2E1 AND 2B1 2 ACTIVITIES IN RATS/

Cytochrome P450 (CYP) 2E1 activity is induced after 24 h of fasting bu t no information is available for shorter fasting periods. We investig ated the induction of CYP 2E1, 2B1/2 and 1A1 in young adult male F344 rats after 8, 16 and 24 h of fasting compared to control. Liver micros omes were analyzed for the following enzyme activities: p-nitrophenol hydroxylase (PNP) for CYP 2E1, pentoxyresorufin-O-dealkylase (PROD) fa r CYP 2B1/2 and ethoxyresorufin-O-deethylase (EROD) for CYP 1A1. After each fasting interval, the activities per mg microsomal protein for P NP and PROD increased but the activity of EROD remained unchanged. Wes tern blots for CYP 2E1 and CYP 2B1 showed increases comparable to the PNP and PROD activities, respectively. On a whole organ basis, increas es were found for PNP and PROD activities, while decreases were found for EROD activity and total microsomal protein. The results are consis tent with an induction of CYP 2E1 and CYP 2B1/2 activities after as li ttle as 8 h of fasting.