Age dependent differential effects of cigarette smoke on hepatic and pulmonary xenobiotic metabolizing enzymes in rats.

Abstract

The effects of cigarette smoke (CS) on hepatic and pulmonary monooxygenase (MO) activities (aniline 4-hydroxylase, AH; aminopyrine N-demethylase, AMND; 7-ethoxyresorufin O-deethylase, EROD; p-nitroanisole O-demethylase, p-NAOD), lipid peroxidation (LP), and reduced glutathione (GSH) levels and glutathione S-transferase (GST) activities toward several substrates (1-chloro-2,4-dinitrobenzene, CDNB; 1,2-dichloro-4-nitrobenzene, DCNB; ethacrynic acid, EAA; 1,2-epoxy-3-(p-nitrophenoxy)-propane, ENPP) were determined in 20-, 90- and 360-day-old male rats. The animals were exposed to CS five times a day, with 1 h intervals, for 3 days in a chamber supplied alternatively with smoke and fresh air, and were killed 16 h after the last treatments. The hepatic AH activity increased significantly in 20-day-old rats and remained unaltered in older age groups. The hepatic AMND activity unaltered, significantly increased and decreased in 20-, 90- and 360-day-old rats, respectively. The pulmonary AH activity increased significantly in 20- and 90-day-old rats whereas no alteration was noted in 360-day-old rats. CS was ineffective on pulmonary AMND activity at all ages. CS increased hepatic and pulmonary EROD and p-NAOD activities significantly in all age groups compared to controls. In liver, LP level was significantly increased, decreased, and unaltered in 20-, 90- and 360-day-old rats, respectively. CS increased hepatic GSH level significantly in 90-day-old rats but was not effective in the other age groups. In lung, LP level was increased in 90- and 360-day-old rats and unaltered in 20-day-old rats. CS increased pulmonary GSH level significantly in 90-day-old rats and did not have any effect in the other age groups. The hepatic GST activities toward CDNB and DCNB decreased significantly in 360-day-old rats and were unaltered in the younger age groups. The hepatic GST activity toward EAA was unaltered, significantly increased and decreased in 20-, 90- and 360-day-old rats, respectively. The hepatic GST activity toward ENPP decreased significantly in 20- and 90-day-old rats but was unaltered in the oldest group of rats. In 20-day-old rats, the pulmonary GST activity toward ENPP increased significantly whereas the other GST activities did not alter. In 90-day-old rats, however, CS significantly decreased all the pulmonary GST activities studied. Unaltered DCNB GST, significant increase in EAA GST and decrease in CDNB and ENPP GST activities of lung were noted in 360-day-old rats. These results reveal that the regulation in rats of hepatic and pulmonary MO and GST activities are differentially influenced by CS as a function of age.