Effects of starvation on liver microsomal P450 activity in juvenile Pleuronectes americanus

Recent work has produced evidence to support the existence of a cytochrome P450 CYP2E1-like isoform in the marine fish, Pleuronectes americanus (winter flounder) (Wall K, Crivello JF. Toxicol Appl Pharmacol 1998;151:98-104). Starvation has been previously demonstrated to induce CYP2E1 activity (assayed as chlorzozazone-6-hydroxylase activity) in mammals and this study was undertaken to determine the effects of starvation on liver chlorzozaxone-6-hydroxylase and ethoxy-resorufin-O-deethylase activity (a CYP1A1 activity) in juvenile winter flounder liver microsomes. A 2-week starvation period resulted in a statistically significant increase in liver microsomal protein, and a decrease in liver lipid and liver glycogen. Ethoxy-resorufin-O-deethylase activity (pmol/min/mg microsomal protein) was reduced with starvation, chlorzoxazone 6-hydroxylase activity (pmol/min per mg microsomal protein) initially decreased but then increased over controls. When these activities were expressed per gm/liver (to account for the starvation-induced changes in liver microsomal protein), chlorzoxazone 6-hydroxylase activity doubled over control during starvation but ethoxy-resorufin-O-deethylase was not significantly changed. The effects of starvation on liver microsomal chlorzoxazone 6-hydroxylase and ethoxy-resorufin-O-deethylase activities are discussed in the context of the impact of physiological states on the ability of fish to detoxify marine xenobiotics.